UMTS Long Term Evolution, LTE, is the technology of choice for the majority of network operators worldwide for providing mobile broadband data and high-speed internet access to their subscriber base. Due to the high commitment LTE is the innovation platform for the wireless industry for the next decade. This class will provide the basics of this fascinating technology. After attending this course you will have an understanding of OFDM-principles including SC-FDMA as the transmission scheme of choice for the LTE uplink. Multiple antenna technology (MIMO), a fundamental part of LTE, will be explained as well as its impact on the design of device and network architecture. We’ll give a quick introduction into the evolution of this technology including future upgrades of LTE features like multimedia broadcast, location based services and increasing bandwidth through carrier aggregation. The second part of the course will provide an overview including practical examples and exercises on how to test a LTE-capable device while performing standardized RF measurements such as power, signal quality, spectrum and receiver sensitivity. We’ll address how to automate these measurements in a simple and cost-effective way. We will introduce application based testing by demonstrating end-to-end (E2E), throughput and application testing using the Rohde & Schwarz R&S®CMW500 Wideband Radio Communication Tester. Examples of application tests are voice over LTE, VoLTE or Video over LTE.

1. UMTS Long Term Evolution (LTE)
technology intro + evolution
measurement aspects
Reiner Stuhlfauth
Reiner.Stuhlfauth@rohde-schwarz.com
Training Centre
Rohde & Schwarz, Germany
Subject to change – Data without tolerance limits is not binding.
R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG. Trade names are trademarks
of the owners.
 2011 ROHDE & SCHWARZ GmbH & Co. KG
Test & Measurement Division
- Training Center -
ROHDE & SCHWARZ GmbH reserves the copy right to all of any part of these course notes.
Permission to produce, publish or copy sections or pages of these notes or to translate them must first
be obtained in writing from
ROHDE & SCHWARZ GmbH & Co. KG, Training Center, Mühldorfstr. 15, 81671 Munich, Germany

2. Technology evolution path
2005/2006 2007/2008 2009/2010 2011/2012 2013/2014
GSM/ EDGE, 200 kHz EDGEevo VAMOS
DL: 473 kbps DL: 1.9 Mbps Double Speech
GPRS UL: 473 kbps UL: 947 kbps Capacity
UMTS HSDPA, 5 MHz HSPA+, R7 HSPA+, R8 HSPA+, R9 HSPA+, R10
DL: 2.0 Mbps DL: 14.4 Mbps DL: 28.0 Mbps DL: 42.0 Mbps DL: 84 Mbps DL: 84 Mbps
UL: 2.0 Mbps UL: 2.0 Mbps UL: 11.5 Mbps UL: 11.5 Mbps UL: 23 Mbps UL: 23 Mbps
HSPA, 5 MHz
DL: 14.4 Mbps
UL: 5.76 Mbps
LTE (4x4), R8+R9, 20MHz LTE-Advanced R10
DL: 300 Mbps DL: 1 Gbps (low mobility)
UL: 75 Mbps UL: 500 Mbps
1xEV-DO, Rev. 0 1xEV-DO, Rev. A 1xEV-DO, Rev. B
cdma DO-Advanced
1.25 MHz 1.25 MHz 5.0 MHz DL: 32 Mbps and beyond
2000 DL: 2.4 Mbps DL: 3.1 Mbps DL: 14.7 Mbps UL: 12.4 Mbps and beyond
UL: 153 kbps UL: 1.8 Mbps UL: 4.9 Mbps
Fixed WiMAX Mobile WiMAX, 802.16e Advanced Mobile
scalable bandwidth Up to 20 MHz WiMAX, 802.16m
1.25 … 28 MHz DL: 75 Mbps (2x2) DL: up to 1 Gbps (low mobility)
typical up to 15 Mbps UL: 28 Mbps (1x2) UL: up to 100 Mbps
November 2012 | LTE Introduction | 2

3. Why LTE?
Ensuring Long Term Competitiveness of UMTS
l LTE is the next UMTS evolution step after HSPA and HSPA+.
l LTE is also referred to as
EUTRA(N) = Evolved UMTS Terrestrial Radio Access (Network).
l Main targets of LTE:
l Peak data rates of 100 Mbps (downlink) and 50 Mbps (uplink)
l Scaleable bandwidths up to 20 MHz
l Reduced latency
l Cost efficiency
l Operation in paired (FDD) and unpaired (TDD) spectrum
November 2012 | LTE Introduction | 3

4. Peak data rates and real average throughput (UL)
100
58
11,5 15
10
5,76
Data rate in Mbps
5
2 2 1,8
2
0,947
1
0,473 0,7
0,5
0,174 0,153
0,2
0,1 0,1 0,1
0,1
0,03
0,01
GPRS EDGE 1xRTT WCDMA E-EDGE 1xEV-DO 1xEV-DO HSPA HSPA+ LTE 2x2
(Rel. 97) (Rel. 4) (Rel. 99/4) (Rel. 7) Rev. 0 Rev. A (Rel. 5/6) (Rel. 7) (Rel. 8)
Technology
max. peak UL data rate [Mbps] max. avg. UL throughput [Mbps]
November 2012 | LTE Introduction | 4

5. Comparison of network latency by technology
800
158 160
710
700
140
600
120
3G / 3.5G / 3.9G latency
2G / 2.5G latency
500
100
85
400 80
320 70
300 60
46
190
200 40
100 20
30
0 0
GPRS EDGE WCDMA HSDPA HSUPA E-EDGE HSPA+ LTE
(Rel. 97) (Rel. 4) (Rel. 99/4) (Rel. 5) (Rel. 6) (Rel. 7) (Rel. 7) (Rel. 8)
Technology
Total UE Air interface Node B Iub RNC Iu + core Internet
November 2012 | LTE Introduction | 5

6. Round Trip Time, RTT
•ACK/NACK
generation in RNC MSC
TTI
Iub/Iur Iu
~10msec
Serving SGSN
RNC
Node B
TTI
=1msec
MME/SAE Gateway
eNode B
•ACK/NACK
generation in node B
November 2012 | LTE Introduction | 6

7. Major technical challenges in LTE
New radio transmission FDD and
schemes (OFDMA / SC-FDMA) TDD mode
MIMO multiple antenna Throughput / data rate
schemes requirements
Timing requirements Multi-RAT requirements
(1 ms transm.time interval) (GSM/EDGE, UMTS, CDMA)
Scheduling (shared channels, System Architecture
HARQ, adaptive modulation) Evolution (SAE)
November 2012 | LTE Introduction | 7

8. Introduction to UMTS LTE: Key parameters
Frequency
UMTS FDD bands and UMTS TDD bands
Range
1.4 MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz
Channel
bandwidth,
1 Resource 6 15 25 50 75 100
Block=180 kHz Resource Resource Resource Resource Resource Resource
Blocks Blocks Blocks Blocks Blocks Blocks
Modulation Downlink: QPSK, 16QAM, 64QAM
Schemes Uplink: QPSK, 16QAM, 64QAM (optional for handset)
Downlink: OFDMA (Orthogonal Frequency Division Multiple Access)
Multiple Access
Uplink: SC-FDMA (Single Carrier Frequency Division Multiple Access)
Downlink: Wide choice of MIMO configuration options for transmit diversity, spatial
MIMO
multiplexing, and cyclic delay diversity (max. 4 antennas at base station and handset)
technology
Uplink: Multi user collaborative MIMO
Downlink: 150 Mbps (UE category 4, 2x2 MIMO, 20 MHz)
Peak Data Rate 300 Mbps (UE category 5, 4x4 MIMO, 20 MHz)
Uplink: 75 Mbps (20 MHz)
November 2012 | LTE Introduction | 8

9. LTE/LTE-A Frequency Bands (FDD)
E-UTRA Uplink (UL) operating band Downlink (DL) operating band
Operating BS receive UE transmit BS transmit UE receive Duplex Mode
Band FUL_low – FUL_high FDL_low – FDL_high
1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz FDD
2 1850 MHz – 1910 MHz 1930 MHz – 1990 MHz FDD
3 1710 MHz – 1785 MHz 1805 MHz – 1880 MHz FDD
4 1710 MHz – 1755 MHz 2110 MHz – 2155 MHz FDD
5 824 MHz – 849 MHz 869 MHz – 894MHz FDD
6 830 MHz – 840 MHz 875 MHz – 885 MHz FDD
7 2500 MHz – 2570 MHz 2620 MHz – 2690 MHz FDD
8 880 MHz – 915 MHz 925 MHz – 960 MHz FDD
9 1749.9 MHz – 1784.9 MHz 1844.9 MHz – 1879.9 MHz FDD
10 1710 MHz – 1770 MHz 2110 MHz – 2170 MHz FDD
11 1427.9 MHz – 1452.9 MHz 1475.9 MHz – 1500.9 MHz FDD
12 698 MHz – 716 MHz 728 MHz – 746 MHz FDD
13 777 MHz – 787 MHz 746 MHz – 756 MHz FDD
14 788 MHz – 798 MHz 758 MHz – 768 MHz FDD
17 704 MHz – 716 MHz 734 MHz – 746 MHz FDD
18 815 MHz – 830 MHz 860 MHz – 875 MHz FDD
19 830 MHz – 845 MHz 875 MHz – 890 MHz FDD
20 832 MHz - 862 MHz 791 MHz - 821 MHz FDD
21 1447.9 MHz - 1462.9 MHz 1495.9 MHz - 1510.9 MHz FDD
22 3410 MHz - 3500 MHz 3510 MHz - 3600 MHz FDD
November 2012 | LTE Introduction | 9

10. LTE/LTE-A Frequency Bands (TDD)
Uplink (UL) operating band Downlink (DL) operating band
E-UTRA
BS receive UE transmit BS transmit UE receive
Operating Duplex Mode
Band
FUL_low – FUL_high FDL_low – FDL_high
33 1900 MHz – 1920 MHz 1900 MHz – 1920 MHz TDD
34 2010 MHz – 2025 MHz 2010 MHz – 2025 MHz TDD
35 1850 MHz – 1910 MHz 1850 MHz – 1910 MHz TDD
36 1930 MHz – 1990 MHz 1930 MHz – 1990 MHz TDD
37 1910 MHz – 1930 MHz 1910 MHz – 1930 MHz TDD
38 2570 MHz – 2620 MHz 2570 MHz – 2620 MHz TDD
39 1880 MHz – 1920 MHz 1880 MHz – 1920 MHz TDD
40 2300 MHz – 2400 MHz 2300 MHz – 2400 MHz TDD
3400 MHz – 3400 MHz –
41 TDD
3600MHz 3600MHz
November 2012 | LTE Introduction | 10

11. Orthogonal Frequency Division Multiple Access
l OFDM is the modulation scheme for LTE in downlink and
uplink (as reference)
l Some technical explanation about our physical base: radio
link aspects
November 2012 | LTE Introduction | 11

12. What does it mean to use the radio channel?
Using the radio channel means to deal with aspects like:
C
A
D
B
Transmitter Receiver
MPP
Time variant channel
Doppler effect
Frequency selectivity attenuation
November 2012 | LTE Introduction | 12

13. Still the same “mobile” radio problem:
Time variant multipath propagation
A: free space
A: free space
B: reflection
B: reflection
C C: diffraction
C: diffraction
A
D: scattering
D: scattering
D
B
Transmitter Receiver
Multipath Propagation reflection: object is large
and Doppler shift compared to wavelength
scattering: object is
small or its surface
irregular
November 2012 | LTE Introduction | 13

14. Multipath channel impulse response
The CIR consists of L resolvable propagation paths
L 1
h  , t    ai  t  e     i 
ji  t 
i 0
path attenuation path phase path delay
|h|²

delay spread
November 2012 | LTE Introduction | 14

15. Radio Channel – different aspects to discuss
Bandwidth or
Wideband Narrowband
Symbol duration
or t
t
Short symbol Long symbol
duration duration
Channel estimation: Frequency?
Pilot mapping Time?
frequency distance of pilots? Repetition rate of pilots?
November 2012 | LTE Introduction | 15

16. Frequency selectivity - Coherence Bandwidth
Here: substitute with single
power Scalar factor = 1-tap
Frequency selectivity
How to combat
channel influence?
f
Narrowband = equalizer
Can be 1 - tap
Wideband = equalizer
Here: find Must be frequency selective
Math. Equation
for this curve
November 2012 | LTE Introduction | 16

17. Time-Invariant Channel: Scenario
Fixed Scatterer
ISI: Inter Symbol
Interference:
Happens, when
Delay spread >
Symbol time
Successive
Fixed Receiver
symbols Transmitter
will interfere Channel Impulse Response, CIR
Transmitter Receiver collision
Signal Signal
t t
Delay Delay spread
→time dispersive
November 2012 | LTE Introduction | 17

18. Motivation: Single Carrier versus Multi Carrier
TSC
|H(f)| f
Source: Kammeyer; Nachrichtenübertragung; 3. Auflage
1
B
TSC
B
t
|h(t)|
t
l Time Domain
l Delay spread > Symboltime TSC
→ Inter-Symbol-Interference (ISI) → equalization effort
l Frequency Domain
l Coherence Bandwidth Bc < Systembandwidth B
→ Frequency Selective Fading → equalization effort
November 2012 | LTE Introduction | 18

19. Motivation: Single Carrier versus Multi Carrier
TSC
|H(f)| f Source: Kammeyer; Nachrichtenübertragung; 3. Auflage
1
B
B TSC
t
|h(t)|
f t
|H(f)|
B 1
f  
B N TMC
t
TMC  N  TSC
November 2012 | LTE Introduction | 19

20. What is OFDM?
Single carrier
transmission,
e.g. WCDMA
Broadband, e.g. 5MHz for WCDMA
Orthogonal
Frequency
Division
Multiplex
Several 100 subcarriers, with x kHz spacing
November 2012 | LTE Introduction | 20

21. Idea: Wide/Narrow band conversion
ƒ
…
S/P
…
…
H(ƒ) t / Tb t / Ts
h(τ) h(τ)
„Channel
Memory“
τ τ
One high rate signal: N low rate signals:
Frequency selective fading Frequency flat fading
November 2012 | LTE Introduction | 21

22. OFDM signal generation
00 11 10 10 01 01 11 01 …. e.g. QPSK
h*(sinjwt + cosjwt) h*(sinjwt + cosjwt) => Σ h * (sin.. + cos…)
Frequency
time
OFDM
symbol
duration Δt 2012 |
November LTE Introduction | 22

23. COFDM
Mapper
X
+
X
Data
with
OFDM
FEC Σ
.....
symbol
overhead
Mapper
X
+
X
November 2012 | LTE Introduction | 23

24. Fourier Transform, Discrete FT
Fourier Transform

H ( f )   h(t )e 2 j ft
dt ;


h(t )   H ( f )e  2 j ft
df ;

Discrete Fourier Transform (DFT)
N 1 N 1 N 1
n n
H n   hk e 2 j k n / N
  hk cos(2  k )  j  hk sin(2  k );
k 0 k 0 N k 0 N
N 1  2 j k
n
1
hk 
N
H e
n 0
n
N
;
November 2012 | LTE Introduction | 24

25. OFDM Implementation with FFT
(Fast Fourier Transformation)
Transmitter Channel
d(0)
Map
IDFT NFFT
d(1)
P/S
S/P
b (k ) Map
. s(n)
.
.
d(FFT-1)
Map
h(n)
Receiver
d(0)
Demap
n(n)
DFT NFFT
d(1)
P/S
ˆ k
S/P
b( ) Demap
.
r(n)
.
.
d(FFT-1)
Demap
November 2012 | LTE Introduction | 25

26. Inter-Carrier-Interference (ICI)
10
SMC  f 
0
-10
-20

-30
xx
S
-40
-50
-60
-70
-1 -0.5 0 0.5 1
 
f-2 f-1 f0 f1 f2 f
Problem of MC - FDM ICI
Overlapp of neighbouring subcarriers
→ Inter Carrier Interference (ICI).
Solution
“Special” transmit gs(t) and receive filter gr(t) and frequencies fk allows orthogonal
subcarrier
→ Orthogonal Frequency Division Multiplex (OFDM)
November 2012 | LTE Introduction | 26

27. Rectangular Pulse
A(f)
Convolution
sin(x)/x
t
f
Δt
Δf
time frequency
November 2012 | LTE Introduction | 27

28. Orthogonality
Orthogonality condition: Δf = 1/Δt
Δf
November 2012 | LTE Introduction | 28

29. ISI and ICI due to channel
Symbol l-1 l l+1
 h  n
n Receiver DFT
Window
Delay spread
fade in (ISI) fade out (ISI)
November 2012 | LTE Introduction | 29

30. ISI and ICI: Guard Intervall
Symbol l-1 l l+1
 h  n TG  Delay Spread
n Receiver DFT
Window
Delay spread
Guard Intervall guarantees the supression of ISI!
November 2012 | LTE Introduction | 30

31. Guard Intervall as Cyclic Prefix
Cyclic Prefix
Symbol l-1 l l+1
 h  n TG  Delay Spread
n Receiver DFT
Window
Delay spread
Cyclic Prefix guarantees the supression of ISI and ICI!
November 2012 | LTE Introduction | 31

32. Synchronisation
Cyclic Prefix
OFDM Symbol : l  1 l l 1
CP CP CP CP
Metric
-
Search window
~
n
November 2012 | LTE Introduction | 32

33. DL CP-OFDM signal generation chain
l OFDM signal generation is based on Inverse Fast Fourier Transform
(IFFT) operation on transmitter side:
Data QAM N Useful
1:N OFDM Cyclic prefix
source Modulator symbol IFFT N:1 OFDM
symbols insertion
streams symbols
Frequency Domain Time Domain
l On receiver side, an FFT operation will be used.
November 2012 | LTE Introduction | 33

34. OFDM: Pros and Cons
Pros:
 scalable data rate
 efficient use of the available bandwidth
 robust against fading
 1-tap equalization in frequency domain
Cons:
 high crest factor or PAPR. Peak to average power ratio
 very sensitive to phase noise, frequency- and clock-offset
 guard intervals necessary (ISI, ICI) → reduced data rate
November 2012 | LTE Introduction | 34

35. MIMO =
Multiple Input Multiple Output Antennas
November 2012 | LTE Introduction | 35

36. MIMO is defined by the number of Rx / Tx Antennas
and not by the Mode which is supported Mode
1 1 SISO Typical todays wireless Communication System
Single Input Single Output
Transmit Diversity
1 1 MISO l Maximum Ratio Combining (MRC)
l Matrix A also known as STC
M
Multiple Input Single Output
l Space Time / Frequency Coding (STC / SFC)
Receive Diversity
1 1
SIMO l Maximum Ratio Combining (MRC)
Single Input Multiple Output Receive / Transmit Diversity
M
Spatial Multiplexing (SM) also known as:
l Space Division Multiplex (SDM)
l True MIMO
1 1 MIMO l Single User MIMO (SU-MIMO)
Multiple Input Multiple Output l Matrix B
M M
Space Division Multiple Access (SDMA) also known as:
l Multi User MIMO (MU MIMO)
l Virtual MIMO
Definition is seen from Channel l Collaborative MIMO
Multiple In = Multiple Transmit Antennas Beamforming
November 2012 | LTE Introduction | 36

37. MIMO modes in LTE
-Spatial Multiplexing
-Tx diversity
-Multi-User MIMO
-Beamforming
-Rx diversity
Increased
Increased
Throughput per
Throughput at
Better S/N UE
Node B
November 2012 | LTE Introduction | 37

38. RX Diversity
Maximum Ratio Combining depends on different fading of the
two received signals. In other words decorrelated fading
channels
November 2012 | LTE Introduction | 38

39. TX Diversity: Space Time Coding
Fading on the air interface
data
The same signal is transmitted at differnet
antennas
space Aim: increase of S/N ratio 
increase of throughput
 s1  s2 
*
S2   * 
Alamouti Coding = diversity gain
time
approaches
 s2 s1  RX diversity gain with MRRC!
Alamouti Coding -> benefit for mobile communications
November 2012 | LTE Introduction | 39

40. MIMO Spatial Multiplexing
C=B*T*ld(1+S/N)
SISO:
Single Input
Single Output
Higher capacity without additional spectrum!
MIMO: S
C   T  B  ld (1  ) ?
min( N T , N R )
i
i
i 1
N
Multiple Input i
Multiple Output
Increasing
capacity per cell
November 2012 | LTE Introduction | 40

41. The MIMO promise
l Channel capacity grows linearly with antennas 
Max Capacity ~ min(NTX, NRX)
l Assumptions 
l Perfect channel knowledge
l Spatially uncorrelated fading
l Reality 
l Imperfect channel knowledge
l Correlation ≠ 0 and rather unknown
November 2012 | LTE Introduction | 41

42. Spatial Multiplexing
Coding Fading on the air interface
data
data
Throughput: <200%
200%
100%
Spatial Multiplexing: We increase the throughput
but we also increase the interference!
November 2012 | LTE Introduction | 42

43. Introduction – Channel Model II Correlation of
propagation
h11
pathes
h21
s1 r1
hMR1
h12
s2 h22 r2 estimates
Transmitter hMR2 Receiver
h1MT h2MT
NTx NRx
sNTx hMRMT rNRx
antennas antennas
s H r
Rank indicator
Capacity ~ min(NTX, NRX) → max. possible rank!
But effective rank depends on channel, i.e. the
correlation situation of H
November 2012 | LTE Introduction | 43

44. Spatial Multiplexing prerequisites
Decorrelation is achieved by:
l Decorrelated data content on each spatial stream difficult
l Large antenna spacing Channel
condition
l Environment with a lot of scatters near the antenna
(e.g. MS or indoor operation, but not BS)
Technical
l Precoding assist
But, also possible
that decorrelation
l Cyclic Delay Diversity is not given
November 2012 | LTE Introduction | 44

45. MIMO: channel interference + precoding
MIMO channel models: different ways to combat against
channel impact:
I.: Receiver cancels impact of channel
II.: Precoding by using codebook. Transmitter assists receiver in
cancellation of channel impact
III.: Precoding at transmitter side to cancel channel impact
November 2012 | LTE Introduction | 45

46. MIMO: Principle of linear equalizing
R = S*H + n
Transmitter will send reference signals or pilot sequence
to enable receiver to estimate H.
n H-1
Rx
s r ^
r
Tx H
LE
The receiver multiplies the signal r with the
Hermetian conjugate complex of the transmitting
function to eliminate the channel influence.
November 2012 | LTE Introduction | 46

47. Linear equalization – compute power increase
h11 H = h11
SISO: Equalizer has to estimate 1 channel
h11
h12 h11 h12
H=
h21 h22
h21 h22
2x2 MIMO: Equalizer has to estimate 4 channels
November 2012 | LTE Introduction | 47

48. transmission – reception model
noise
s + r
A H R
transmitter channel receiver
•Modulation, •detection,
•Power •estimation
•„precoding“, •Eliminating channel
•etc. Linear equalization impact
at receiver is not •etc.
very efficient, i.e.
noise can not be cancelled
November 2012 | LTE Introduction | 48

49. MIMO – work shift to transmitter
Channel Receiver
Transmitter
November 2012 | LTE Introduction | 49

50. MIMO Precoding in LTE (DL)
Spatial multiplexing – Code book for precoding
Code book for 2 Tx:
Codebook Number of layers 
index
1 2 Additional multiplication of the
1  1 1 0
0 0 
 
 
2 0 1 
layer symbols with codebook
0  1 1 1  entry
1 1   
  2 1 1
1 1 1 1 1 
2   
2 1 2  j  j
1 1
3   -
2 1
1 1 
4   -
2  j
1 1
5   -
2  j 
November 2012 | LTE Introduction | 50

51. MIMO precoding
precoding
Ant1
Ant2 t
+
 1
2 1 ∑
t
+
1
precoding -1
1
∑=0
t
t
November 2012 | LTE Introduction | 51

52. MIMO – codebook based precoding
Precoding
codebook
noise
s + r
A H R
transmitter channel receiver
Precoding Matrix Identifier, PMI
Codebook based precoding creates
some kind of „beamforming light“
November 2012 | LTE Introduction | 52

53. MIMO: avoid inter-channel interference – future outlook
e.g. linear precoding:
V1,k Y=H*F*S+V
S Link adaptation
+
Transmitter H Space time
F receiver
xk +
yk
VM,k
Feedback about H
Idea: F adapts transmitted signal to current channel conditions
November 2012 | LTE Introduction | 53

54. MAS: „Dirty Paper“ Coding – future outlook
l Multiple Antenna Signal Processing: „Known Interference“
l Is like NO interference
l Analogy to writing on „dirty paper“ by changing ink color accordingly
„Known
„Known „Known „Known
Interference
Interference Interference Interference
is No
is No is No is No
Interference“
Interference“ Interference“ Interference“
November 2012 | LTE Introduction | 54

55. Spatial Multiplexing
Codeword Fading on the air interface
data
Codeword
data
Spatial Multiplexing: We like to distinguish the 2 useful
Propagation passes:
How to do that? => one idea is SVD
November 2012 | LTE Introduction | 55

56. Idea of Singular Value Decomposition
s1 MIMO r1
know
r=Hs+n s2 r2
channel H
Singular Value
Decomposition
~
s1 ~
r1
SISO
wanted ~ ~
s2 r2
~ ~ ~
r=Ds+n
channel D
November 2012 | LTE Introduction | 56

57. Singular Value Decomposition (SVD)
r=Hs+n
H = U Σ (V*)T
U = [u1,...,un] eigenvectors of (H*)T H
V = [v1,...,vm] eigenvectors of H (H*)T
 1 0 0 
0  i eigenvalues of (H*)T H
 0 0

 2
 0 0 3  singular values  i  i
 0
 0  ~ = (U*)T r
r
~
~= Σ s + n
r ~ ~ s = (V*)T s
~ = (U*)T n
n
November 2012 | LTE Introduction | 57

58. MIMO: Signal processing considerations
MIMO transmission can be expressed as
r = Hs+n which is, using SVD = UΣVHs+n
n1
s1 σ1 r1
V U Σ VH n2 UH
s2 σ2 r2
Imagine we do the following:
1.) Precoding at the transmitter:
Instead of transmitting s, the transmitter sends s = V*s
2.) Signal processing at the receiver
Multiply the received signal with UH, r = r*UH
So after signal processing the whole signal can be expressed as:
r =UH*(UΣVHVs+n)=UHU Σ VHVs+UHn = Σs+UHn
=InTnT =InTnT
November 2012 | LTE Introduction | 58

59. MIMO: limited channel feedback
Transmitter H Receiver
n1
s1 σ1 r1
V U Σ VH n2 UH
s2 σ2 r2
Idea 1: Rx sends feedback about full H to Tx.
-> but too complex,
-> big overhead
-> sensitive to noise and quantization effects
Idea 2: Tx does not need to know full H, only unitary matrix V
-> define a set of unitary matrices (codebook) and find one matrix in the codebook that
maximizes the capacity for the current channel H
-> these unitary matrices from the codebook approximate the singular vector structure
of the channel
=> Limited feedback is almost as good as ideal channel knowledge feedback
November 2012 | LTE Introduction | 59

60. Cyclic Delay Diversity, CDD
A2
A1 Amp
litud
D
e
Transmitter B
Delay Spread Time
Delay
Multipath propagation
precoding
+
 +
precoding Time
No multipath propagation Delay
November 2012 | LTE Introduction | 60

61. „Open loop“ und „closed loop“ MIMO
Open loop (No channel knowledge at transmitter)
r  Hs  n Channel
Status, CSI
Rank indicator
Closed loop (With channel knowledge at transmitter
r  HWs  n Channel
Status, CSI
Rank indicator
Adaptive Precoding matrix („Pre-equalisation“)
Feedback from receiver needed (closed loop)
November 2012 | LTE Introduction | 61

62. MIMO transmission modes
Transmission mode2
Transmission mode3
TX diversity
Transmission mode1 Open-loop spatial
SISO multiplexing
7 transmission
Transmission mode4 Transmission mode7
Closed-loop spatial modes are SISO, port 5
multiplexing defined = beamforming in TDD
Transmission mode6
Transmission mode5 Closed-loop
Multi-User MIMO spatial multiplexing,
using 1 layer
Transmission mode is given by higher layer IE: AntennaInfo
November 2012 | LTE Introduction | 62

63. Beamforming
Closed loop precoded
Adaptive Beamforming beamforming
•Classic way •Kind of MISO with channel
knowledge at transmitter
•Antenna weights to adjust beam
•Precoding based on feedback
•Directional characteristics
•No specific antenna
•Specific antenna array geometrie
array geometrie
•Dedicated pilots required •Common pilots are sufficient
November 2012 | LTE Introduction | 63

64. Spatial multiplexing vs beamforming
Spatial multiplexing increases throughput, but looses coverage
November 2012 | LTE Introduction | 64

65. Spatial multiplexing vs beamforming
Beamforming increases coverage
November 2012 | LTE Introduction | 65

66. Basic OFDM parameter
LTE
1
f  15 kHz 
T
Fs  N FFT  f
N FFT
Fs   3.84Mcps
256
f
NFFT  2048
Coded symbol rate= R
Sub-carrier CP
S/P Mapping IFFT insertion
N TX Data symbols
Size-NFFT
November 2012 | LTE Introduction | 66

67. LTE Downlink:
Downlink slot and (sub)frame structure
Symbol time, or number of symbols per time slot is not fixed
One radio frame, Tf = 307200Ts=10 ms
One slot, Tslot = 15360Ts = 0.5 ms
#0 #1 #2 #3 #18 #19
One subframe
We talk about 1 slot, but the minimum resource is 1 subframe = 2 slots !!!!!
Ts  1 15000  2048
Ts = 32.522 ns
November 2012 | LTE Introduction | 67

68. Resource block definition
1 slot = 0,5msec
Resource block
=6 or 7 symbols
In 12 subcarriers
12 subcarriers
Resource element
DL UL
N symb or N symb
6 or 7,
Depending on
cyclic prefix
November 2012 | LTE Introduction | 68

69. LTE Downlink
OFDMA time-frequency multiplexing
frequency
QPSK, 16QAM or 64QAM modulation
UE4
1 resource block =
180 kHz = 12 subcarriers UE5
UE3
UE2
UE6
Subcarrier spacing = 15 kHz time
UE1
1 subframe =
*TTI = transmission time interval 1 slot = 0.5 ms = 1 ms= 1 TTI*=
** For normal cyclic prefix duration 7 OFDM symbols** 1 resource block pair
November 2012 | LTE Introduction | 69

70. LTE: new physical channels for data and control
Physical Control Format Indicator Channel PCFICH:
Indicates Format of PDCCH
Physical Downlink Control Channel PDCCH:
Downlink and uplink scheduling decisions
Physical Downlink Shared Channel PDSCH: Downlink data
Physical Hybrid ARQ Indicator Channel PHICH:
ACK/NACK for uplink packets
Physical Uplink Shared Channel PUSCH: Uplink data
Physical Uplink Control Channel PUCCH:
ACK/NACK for downlink packets, scheduling requests, channel quality info
November 2012 | LTE Introduction | 70

71. LTE Downlink: FDD channel mapping example
Subcarrier #0 RB
November 2012 | LTE Introduction | 71

72. LTE Downlink:
baseband signal generation
code words layers antenna ports
Modulation OFDM OFDM signal
Scrambling
Mapper Mapper generation
Layer
Precoding
Mapper
Modulation OFDM OFDM signal
Scrambling
Mapper Mapper generation
1 stream =
several
Avoid QPSK For MIMO Weighting 1 OFDM subcarriers,
constant 16 QAM Split into data symbol per based on
sequences 64 QAM Several streams for stream Physical
streams if MIMO ressource
needed blocks
November 2012 | LTE Introduction | 72

73. Adaptive modulation and coding
Transportation block size
User data FEC
Flexible ratio between data and FEC = adaptive coding
November 2012 | LTE Introduction | 73

74. Channel Coding Performance
November 2012 | LTE Introduction | 74

75. Automatic repeat request, latency aspects
•Transport block size = amount of
data bits (excluding redundancy!)
•TTI, Transmit Time Interval = time
duration for transmitting 1 transport
block
Transport block
Round
Trip
Time
ACK/NACK
Network UE
Immediate acknowledged or non-acknowledged
feedback of data transmission
November 2012 | LTE Introduction | 75

76. HARQ principle: Multitasking
Δt = Round trip time
Tx Data Data Data Data Data Data Data Data Data Data
ACK/NACK
Demodulate, decode, descramble,
Rx FFT operation, check CRC, etc.
process
ACK/NACK
Processing time for receiver
Rx Demodulate, decode, descramble,
process FFT operation, check CRC, etc.
t
Described as 1 HARQ process
November 2012 | LTE Introduction | 76

77. LTE Round Trip Time RTT
n+4 n+4 n+4
ACK/NACK
PDCCH
PHICH
Downlink
HARQ
Data
Data
UL
Uplink
t=0 t=1 t=2 t=3 t=4 t=5 t=6 t=7 t=8 t=9 t=0 t=1 t=2 t=3 t=4 t=5
1 frame = 10 subframes
8 HARQ processes
RTT = 8 msec
November 2012 | LTE Introduction | 77

78. HARQ principle: Soft combining
1st transmission with puncturing scheme P1
l T i is a e am l o h n e co i g
2nd transmission with puncturing scheme P2
l hi i n x m le f cha n l c ing
Soft Combining = Σ of transmission 1 and 2
l Thi is an exam le of channel co ing
Final decoding
lThis is an example of channel coding
November 2012 | LTE Introduction | 78

79. Hybrid ARQ
Chase Combining = identical retransmission
Turbo Encoder output (36 bits)
Systematic Bits
Parity 1
Parity 2
Transmitted Bit Rate Matching to 16 bits (Puncturing)
Original Transmission Retransmission
Systematic Bits
Parity 1
Parity 2
Punctured Bit Chase Combining at receiver
Systematic Bits
Parity 1
Parity 2
November 2012 | LTE Introduction | 79

80. Hybrid ARQ
Incremental Redundancy
Turbo Encoder output (36 bits)
Systematic Bits
Parity 1
Parity 2
Rate Matching to 16 bits (Puncturing)
Original Transmission Retransmission
Systematic Bits
Parity 1
Parity 2
Punctured Bit Incremental Redundancy Combining at receiver
Systematic Bits
Parity 1
Parity 2
November 2012 | LTE Introduction | 80

81. LTE Physical Layer:
SC-FDMA in uplink
Single Carrier Frequency Division
Multiple Access
November 2012 | LTE Introduction | 81

82. LTE Uplink:
How to generate an SC-FDMA signal in theory?
Coded symbol rate= R
Sub-carrier CP
DFT Mapping IFFT insertion
NTX symbols
Size-NTX Size-NFFT
 LTE provides QPSK,16QAM, and 64QAM as uplink modulation schemes
 DFT is first applied to block of NTX modulated data symbols to transform them into
frequency domain
 Sub-carrier mapping allows flexible allocation of signal to available sub-carriers
 IFFT and cyclic prefix (CP) insertion as in OFDM
 Each subcarrier carries a portion of superposed DFT spread data symbols
 Can also be seen as “pre-coded OFDM” or “DFT-spread OFDM”
November 2012 | LTE Introduction | 82

83. LTE Uplink:
How does the SC-FDMA signal look like?
 In principle similar to OFDMA, BUT:
 In OFDMA, each sub-carrier only carries information related to one specific symbol
 In SC-FDMA, each sub-carrier contains information of ALL transmitted symbols
November 2012 | LTE Introduction | 83

84. LTE uplink
SC-FDMA time-frequency multiplexing
1 resource block =
180 kHz = 12 subcarriers Subcarrier spacing = 15 kHz
frequency
UE1 UE2 UE3
1 slot = 0.5 ms =
7 SC-FDMA symbols**
1 subframe =
1 ms= 1 TTI*
UE4 UE5 UE6
*TTI = transmission time interval
** For normal cyclic prefix duration
time QPSK, 16QAM or 64QAM modulation
November 2012 | LTE Introduction | 84

85. LTE Uplink:
baseband signal generation
UE specific
Scrambling code
Modulation Transform Resource SC-FDMA
Scrambling element mapper
mapper precoder signal gen.
Mapping on
physical 1 stream =
Discrete
Ressource, several
Avoid QPSK Fourier
i.e. subcarriers,
constant 16 QAM Transform
subcarriers based on
sequences 64 QAM not used for Physical
(optional) reference ressource
signals blocks
November 2012 | LTE Introduction | 85

86. LTE evolution
LTE Rel. 9 features
LTE Advanced
November 2012 | LTE Introduction | 86

87. The LTE evolution Rel-9
eICIC
enhancements
Relaying
In-device Rel-10
Diverse Data co-existence
Application CoMP
Rel-11
Relaying
eICIC
eMBMS
enhancements SON
enhancements
MIMO 8x8 MIMO 4x4
Carrier Enhanced
Aggregation SC-FDMA
Public Warning
Positioning System Home eNodeB
Self Organizing
eMBMS Networks
DL UL
Multi carrier /
Dual Layer DL UL Multi-RAT
Beamforming Base Stations
LTE Release 8
FDD / TDD
November 2012 | LTE Introduction | 87

88. What are antenna ports?
l 3GPP TS 36.211(Downlink)
“An antenna port is defined such that the channel over which a symbol on the
antenna port is conveyed can be inferred from the channel over which another
symbol on the same antenna port is conveyed.”
l What does that mean?
l The UE shall demodulate a received signal – which is transmitted over a
certain antenna port – based on the channel estimation performed on the
reference signals belonging to this (same) antenna port.
November 2012 | LTE Introduction | 88

89. What are antenna ports?
l Consequences of the definition
l There is one sort of reference signal per antenna port
l Whenever a new sort of reference signal is introduced by 3GPP (e.g. PRS),
a new antenna port needs to be defined (e.g. Antenna Port 6)
l 3GPP defines the following antenna port / reference signal
combinations for downlink transmission:
l Port 0-3: Cell-specific Reference Signals (CS-RS)
l Port 4: MBSFN-RS
l Port 5: UE-specific Reference Signals (DM-RS): single layer (TX mode 7)
l Port 6: Positioning Reference Signals (PRS)
l Port 7-8: UE-specific Reference Signals (DM-RS): dual layer (TX mode 8)
l Port 7-14: UE specific Referene Signals for Rel. 10
l Port 15 – 22: CSI specific reference signals, channel status info in Rel. 10
November 2012 | LTE Introduction | 89

90. What are antenna ports?
l Mapping „Antenna Port“ to „Physical Antennas“
Antenna Port Physical Antennas
1
AP0 PA0
AP1 1 W5,0
AP2 1 PA1
W5,1
AP3 1
PA2
AP4 … W5,2
W5,3
AP5 PA3
…
AP6
AP7 …
AP8 …
The way the "logical" antenna ports are mapped to the "physical" TX antennas lies
completely in the responsibility of the base station. There's no need for the base station
to tell the UE.
November 2012 | LTE Introduction | 90

91. LTE antenna port definition
Antenna ports are linked to the reference signals
-> one example:
Normal CP
Cell Specific RS
PA -RS
PCFICH /PHICH /PDCCH
PUSCH or No Transmission
UE in connected mode, scans
UE in idle mode, scans for Positioning RS on antenna port 6
Antenna port 0, cell specific RS to locate its position
November 2012 | LTE Introduction | 91

92. Multimedia Broadcast Messaging Services, MBMS
Broadcast: Unicast:
Public info for Private info for dedicated user
everybody
Multicast:
Common info for
User after authentication
November 2012 | LTE Introduction | 92

93. LTE MBMS architecture
November 2012 | LTE Introduction | 93

94. MBMS in LTE
MBMS
MME
GW
|
M3 MBMS GW: MBMS Gateway
MCE: Multi-Cell/Multicast Coordination Entity
M1
|
MCE M1: user plane interface
M2: E-UTRAN internal control plane interface
M2 M3: control plane interface between E-UTRAN and EPC
|
eNB
Logical architecture for MBMS
November 2012 | LTE Introduction | 94

95. MBSFN – MBMS Single Frequency Network
Mobile communication network Single Frequency Network
each eNode B sends individual each eNode B sends identical
signals signals
November 2012 | LTE Introduction | 95

96. MBSFN
If network is synchronised,
Signals in downlink can be
combined
November 2012 | LTE Introduction | 96

97. evolved Multimedia Broadcast Multicast Services
Multimedia Broadcast Single Frequency Network (MBSFN) area
l Useful if a significant number of users want to consume the same data
content at the same time in the same area!
l Same content is transmitted in a specific area is known as MBSFN area.
l Each MBSFN area has an own identity (mbsfn-AreaId 0…255) and can consists of
multiple cells; a cell can belong to more than one MBSFN area.
l MBSFN areas do not change dynamically over time.
MBSFN area 0 MBSFN area 255
11
3 8 13
MBSFN reserved cell.
1 6 12 15
A cell within the MBSFN
area, that does not support 4 9 14
MBMS transmission.
2 7 13
5 10
A cell can belong to
MBSFN area 1
more than one MBSFN
area; in total up to 8.
November 2012 | LTE Introduction | 97

98. eMBMS
Downlink Channels
l Downlink channels related to MBMS
l MCCH Multicast Control Channel
l MTCH Multicast Traffic Channel
l MCH Multicast Channel
l PMCH Physical Multicast Channel
l MCH is transmitted over MBSFN in
specific subrames on physical layer
l MCH is a downlink only channel (no HARQ, no RLC repetitions)
l Higher Layer Forward Error Correction (see TS26.346)
l Different services (MTCHs and MCCH) can be multiplexed
November 2012 | LTE Introduction | 98

99. eMBMS channel mapping
Subframes 0,4,5 and 9 are not MBMS, because
Of paging occasion can occur here
Subframes 0 and 5 are not MBMS, because
of PBCH and Sync Channels
November 2012 | LTE Introduction | 99

100. eMBMS allocation based on SIB2 information
011010
Reminder:
Subframes
0,4,5, and 9
Are non-MBMS
November 2012 | LTE Introduction | 100

101. eMBMS: MCCH position according to SIB13
November 2012 | LTE Introduction | 101

102. LTE Release 9
Dual-layer beamforming
l 3GPP Rel-8 – Transmission Mode 7 = beamforming without
UE feedback, using UE-specific reference signal pattern,
l Estimate the position of the UE (Direction of Arrival, DoA),
l Pre-code digital baseband to direct beam at direction of arrival,
l BUT single-layer beamforming, only one codeword (TB),
l 3GPP Rel-9 – Transmission Mode 8 = beamforming with or
without UE feedback (PMI/RI) using UE-specific reference
signal pattern, but dual-layer,
l Mandatory for TDD, optional for FDD,
l 2 (new) reference signal pattern for two new antenna ports 7 and 8,
l New DCI format 2B to schedule transmission mode 8,
l Performance test in 3GPP TS 36.521 Part 1 (Rel-9) are adopted to
support testing of transmission mode 8.
November 2012 | LTE Introduction | 102

103. LTE Release 9
Dual-layer beamforming – Reference Symbol Details
l Cell specific
antenna port 0 and
antenna port 1
reference symbols
Antenna Port 0 Antenna Port 1
l UE specific antenna
port 7 and antenna
port 8 reference
symbols
Antenna Port 7 Antenna Port 8
November 2012 | LTE Introduction | 103

104. 2 layer beamforming
throughput
Spatial multiplexing: increase throughput but less coverage
1 layer beamforming: increase coverage
SISO: coverage and throughput, no increase
2 layer beamforming
Increases throughput and
coverage
coverage
Spatial multiplexing increases throughput, but looses coverage
November 2012 | LTE Introduction | 104

105. Location based services
l Location Based Services“
l Products and services which need location
information
l Future Trend:
Augmented Reality
November 2012 | LTE Introduction | 105

106. Where is Waldo?
November 2012 | LTE Introduction | 106

107. Location based services
The idea is not new, … so what to discuss?
Satellite based services
Location
controller
Network based services
Who will do the measurements? The UE or the network? = „assisted“
Who will do the calculation? The UE or the network? = „based“
So what is new?
Several ideas are defined and hybrid mode is possible as well,
Various methods can be combined.
November 2012 | LTE Introduction | 107

108. E-UTRA supported positioning methods
November 2012 | LTE Introduction | 108

109. E-UTRA supported positioning network architecture
Control plane and user plane signaling
LCS4)
Client
S1-U Serving S5 Packet Lup
SUPL / LPP Gateway Gateway SLP1)
(S-GW) (P-GW) LCS
Server (LS) SLs
LPPa
LPP Mobile
Management E-SMLC2) GMLC3)
S1-MME SLs
Entity (MME)
LTE-capable device LTE base station
User Equipment, UE eNodeB (eNB)
(LCS Target)
Secure User Plane
Location positioning SUPL= user plane
protocol LPP = signaling
control plane 1) SLP – SUPL Location Platform, SUPL – Secure User Plane Location
2) E-SMLC – Evolved Serving Mobile Location Center
signaling 3) GMLC – Gateway Mobile Location Center
4) LCS – Location Service
5) 3GPP TS 36.455 LTE Positioning Protocol Annex (LPPa)
6) 3GPP TS 36.355 LTE Positioning Protocol (LPP)
November 2012 | LTE Introduction | 109

110. E-UTRAN UE Positioning Architecture
l In contrast to GERAN and UTRAN, the E-UTRAN positioning
capabilities are intended to be forward compatible to other access
types (e.g. WLAN) and other positioning methods (e.g. RAT uplink
measurements).
l Supports user plane solutions, e.g. OMA SUPL 2.0
UE = User Equipment
SUPL* = Secure User Plane Location
OMA* = Open Mobile Alliance
SET = SUPL enabled terminal
SLP = SUPL locaiton platform
E-SMLC = Evolved Serving Mobile
Location Center
MME = Mobility Management Entity
RAT = Radio Access Technology
*www.openmobilealliance.org/technical/release_program/supl_v2_0.aspx
November 2012 | LTE Introduction | 110 Source: 3GPP TS 36.305

111. Global Navigation Satellite Systems
l GNSS – Global Navigation Satellite Systems; autonomous
systems: l GNSS are designed for
l GPS – USA 1995. continuous
l GLONASS – Russia, 2012. reception, outdoors.
l Gallileo – Europe, target 201?. l Challenging environments:
l Compass (Beidou) – China, under urban, indoors, changing
development, target 2015. locations.
l IRNSS – India, planning process.
E5a E1
L5 L5b L2 G2 E6 L1 G1
1164 1215 1237 1260 1300 1559 1591 f [MHz]
1563 1587 1610
GALLILEO GPS GLONASS
Signal fCarrier [MHz] Signal fCarrier [MHz] Signal fCarrier [MHz]
1602±k*0,562
E1 1575,420 L1C/A 1575,420 G1
5
1246±k*0,562
E6 1278,750 L1C 1575,420 G2
5
E5 1191,795 L2C 1227,600 k = -7 … 13
E5a 1176,450 L5 1176,450
http://www.hindawi.com/journals/ijno/2010/812945/
E5b 1207,140
November 2012 | LTE Introduction | 111

112. LTE Positioning Protocol (LPP) 3GPP TS 36.355
LPP position methods
- A-GNSS Assisted Global Navigation Satellite System
- E-CID Enhanced Cell ID
LTE radio - OTDOA Observed time differerence of arrival
signal
*GNSS and LTE radio signals
eNB
Measurements based on reference sources*
Target LPP
Location
Device Server
Assistance data
LPP over RRC
UE Control plane solution E-SMLC Enhanced Serving
Mobile Location Center
LPP over SUPL
SUPL enabled
Terminal
SET User plane solution SLP SUPL location
platform
November 2012 | LTE Introduction | 112

113. GNSS positioning methods supported
l Autonomeous GNSS
l Assisted GNSS (A-GNSS)
l The network assists the UE GNSS receiver to
improve the performance in several aspects:
– Reduce UE GNSS start-up and acquisition times
– Increase UE GNSS sensitivity
– Allow UE to consume less handset power
l UE Assisted
– UE transmits GNSS measurement results to E-SMLC where the position calculation
takes place
l UE Based
– UE performs GNSS measurements and position calculation, suppported by data …
– … assisting the measurements, e.g. with reference time, visible satellite list etc.
– … providing means for position calculation, e.g. reference position, satellite ephemeris, etc.
November 2012 | LTE Introduction | 113 Source: 3GPP TS 36.305

114. GNSS band allocations
E5a E1
L5 E5b L2 G2 E6 L1 G1 f/MHz
1164 1215 1237 1260 1300 1559 1563 1587 1591 1610
November 2012 | LTE Introduction | 114

115. GPS and GLONASS satellite orbits
GPS:
26 Satellites
Orbital radius 26560 km
GLONASS:
26 Satellites
Orbital radius 25510 km
November 2012 | LTE Introduction | 115

116. Why is GNSS not sufficent?
Critical scenario Very critical scenario GPS Satellites visibility (Urban)
l Global navigation satellite systems (GNSSs) have restricted
performance in certain environments
l Often less than four satellites visible: critical situation for GNSS
positioning
 support required (Assisted GNSS)
 alternative required (Mobile radio positioning)
Reference [DLR]
November 2012 | LTE Introduction | 116