3. 3
AT&T Test
• AT&T launched its LTE network in 5 cities on 9/18/11
• PC Magazine article: AT&T vs. Verizon: LTE, Head-to-Head
http://www.pcmag.com/article2/0,2817,2393182,00.asp#fbid
=fD0LlOUpHzx
Unable to roam between AT&T and Verizon LTE networks
AT&T has put coverage maps on its site advocating merger
with T-Mobile
Dallas-Fort Worth
San Antonio
Houston
Atlanta
Chicago
www.octoscope.com
7. 7
What’s eHRPD?
• eHRPD is Verizon’s 3G; upgrade path to LTE
CDMA based; enhanced HRPD (EVDO )
Maintains the same private IP when handset moves from tower to tower
Reduces dropped sessions and decreases the handover latency
• eHRPD will be used by Verizon for VOIP calls until 2020
eHRPD = enhanced high rate packet data
EVDO = Evolution-Data Optimized www.octoscope.com
8. 8
3G Network Latency
• HSPA+ is aimed at extending operators’ investment in HSPA
2x2 MIMO, 64 QAM in the downlink, 16 QAM in the uplink
Data rates up to 42 MB in the downlink and 11.5 MB in the uplink.
Traditional HSPA One tunnel HSPA One tunnel HSPA+
GGSN GGSN Gateway GGSN One-tunnel architecture
GPRS flattens the network by
Control Support enabling a direct
Data Serving Node
transport path for user
SGSN GPRS SGSN SGSN data between RNC and
Support
the GGSN, thus
Node Radio
minimizing delays and
RNC RNC Network
Controller
set-up time
User RNC
Data
Node B Node B Node B
www.octoscope.com
10. 10
OFDM and MIMO
• OFDM transforms a frequency- and time-
variable fading channel into parallel
correlated flat-fading channels, enabling
wide bandwidth operation
… …
Channel Quality
Frequency
Frequency-variable channel
appears flat over the narrow
band of an OFDM subcarrier.
OFDM = orthogonal frequency division multiplexing
MIMO = multiple input multiple output
www.octoscope.com
11. 11
OFDMA
OFDM is a
modulation
scheme
Time
Time
OFDMA is a LTE
modulation and
access scheme
Frequency
Multiple Access Frequency allocation per Frequency per user is
user is continuous vs. time dynamically allocated vs. time
slots
User 1 User 2 User 3 User 4 User 5
OFDM = orthogonal frequency division multiplexing
OFDMA = orthogonal frequency division multiple access
www.octoscope.com
12. 12
OFDMA vs. SC-FDMA (LTE Uplink)
• Multi-carrier OFDM signal exhibits high
PAPR (Peak to Average Power Ratio) due
to in-phase addition of subcarriers.
• Power Amplifiers (PAs) must
accommodate occasional peaks and this
results low efficiency of PAs, typically
only 15-20% efficient. Low PA efficiency
significantly shortens battery life. In-phase addition
of sub-carriers
• To minimize PAPR, LTE has adapted SC- creates peaks in
FDMA (single carrier OFDM) in the the OFDM signal
uplink. SC-FDMA exhibits 3-6 dB less
PAPR than OFDMA.
www.octoscope.com
13. 13
Multiple Antenna Techniques
• SISO (Single Input Single Output)
Traditional radio
• MISO (Multiple Input Single Output)
Transmit diversity (STBC, SFBC, CDD)
• SIMO (Single Input Multiple Output)
Receive diversity, MRC
• MIMO (Multiple Input Multiple Output)
SM to transmit multiple streams simultaneously; can be used in
conjunction with CDD; works best in high SNR environments and
channels de-correlated by multipath
TX and RX diversity, used independently or together; used to enhance
throughput in the presence of adverse channel conditions
• Beamforming
SM = spatial multiplexing
SFBC = space frequency block coding
STBC = space time block coding
CDD = cyclic delay diversity
MRC = maximal ratio combining
SM = Spatial Multiplexing
SNR = signal to noise ratio
www.octoscope.com
14. 14
MIMO Based RX and TX Diversity
• When 2 receivers are available in a MIMO
radio MRC can be used to combine signals
from two or more antennas, improving Peak
SNR
• MIMO also enables transmit diversity
techniques, including CDD, STBC, SFBC
• TX diversity spreads the signal creating
artificial multipath to decorrelate signals Null
from different transmitters so as to
optimize signal reception
MIMO = multiple input multiple output
SIMO = single input multiple outputs
SM = spatial multiplexing
SFBC = space frequency block coding Delay is inside the TX
STBC = space time block coding
CDD = cyclic delay diversity
MRC = maximal ratio combining
SM = Spatial Multiplexing
SNR = signal to noise ratio
www.octoscope.com
15. 15
Distributed-Input-Distributed-Output (DIDO)
Distributed Antenna System
+
Beamforming
?
Recent white paper from Rearden Companies
+ Beamforming
Distributed Antenna System www.octoscope.com
16. 16
LTE Scalable Channel Bandwidth
Channel bandwidth in MHz
Transmission bandwidth in RBs
Center subcarrier (DC)
not transmitted in DL
Channel bw 1.4 3 5 10 15 20
MHz
Transmission bw 1.08 2.7 4.5 9 13.5 18
# RBs per slot 6 15 25 50 75 100
www.octoscope.com
17. 17
FDD vs. TDD
• FDD (frequency division duplex)
Paired channels
• TDD (time division duplex) TD-LTE
Single frequency channel for uplink an downlink
Is more flexible than FDD in its proportioning of uplink vs. downlink bandwidth utilization
Can ease spectrum allocation issues
DL
UL
DL
UL
www.octoscope.com
19. 19
UHF Spectrum, Including CH 52-59, 692-746 MHz
A B C D E A B C
White Space Bands
Band17 Band17
US (FCC) White Spaces Band12 Band12
54-72, 76-88, 174-216, 470-692 MHz Low 700 MHz band
European (ECC) White Spaces (470-790 MHz)
0 100 200 300 400 500 600 700 800 900 MHz
High 700 MHz band
A B A B
CH 60-69, 746-806 MHz
www.octoscope.com
ECC = Electronic Communications Committee
20. 20
High 700 MHz Band
D-Block
MHz 758 763 775 788 793 805
Band 13 Band 13
Band 14 Band 14
Guard band Guard band
Public Safety Broadband (763-768, 793-798 MHz)
Public Safety Narrowband (769-775, 799-805 MHz), local LMR
LMR = land mobile radio www.octoscope.com
21. 21
TV Channels and White Space Allocation
US – FCC
Channel # Frequency Band
*Channel 37 (608-614 MHz) is
reserved for radio astronomy
2-4 54-72 MHz **Shared with public safety
Fixed 5-6 76-88 MHz VHF
TVBDs
only 7-13 174-216 MHz Transition from NTSC to ATSC
(analog to digital TV) in June 12,
14-20 470-512 MHz** 2009 freed up channels 52-69
(above 692 MHz)
UHF
White Spaces 21-51* 512-692 MHz
http://www.fcc.gov/mb/engineering/usallochrt.pdf
Europe – ECC
Channel # Frequency Band
5-12 174-230 MHz VHF
White Spaces 21-60 470-790 MHz
UHF
61-69 790-862 MHz
www.octoscope.com
22. 22
LTE Frequency Bands - TDD
TD-LTE
Band UL and DL Regions
33 1900 - 1920 MHz Europe, Asia (not Japan)
34 2010 - 2025 MHz Europe, Asia
35 1850 - 1910 MHz
36 1930 - 1990 MHz
37 1910 - 1930 MHz
38 2570 - 2620 MHz Europe
39 1880 - 1920 MHz China
40 2300 – 2400 MHz Europe, Asia
41 2496 – 2690 MHz Americas (Clearwire LTE)
42 3400 – 3600 MHz
43 3600 – 3800 MHz
Source: 3GPP TS 36.104; V10.1.0 (2010-12)
www.octoscope.com
23. 23
WiMAX Frequency Bands - TDD
Band (GHz) Bandwidth Certification Group Code
Class BW (MHZ) (BCG)
1 2.3-2.4
8.75 1.A
5 AND 10 1.B WiMAX Forum
2 2.305-2.320, 2.345-2.360 Mobile
3.5 2.A (Obsolete, replaced by 2.D) Certification Profile
5 2.B (Obsolete, replaced by 2.D) v1.1.0
10 2.C (Obsolete, replaced by 2.D)
A universal
3.5 AND 5 AND 10 2.D
frequency step
3 2.496-2.69
size of 250 KHz is
5 AND 10 3.A
recommended for
4 3.3-3.4
all band classes,
5 4.A
while 200 KHz
7 4.B
step size is also
10 4.C
recommended for
5 3.4-3.8
band class 3 in
5 5.A
Europe.
7 5.B
10 5.C
7 0.698-0.862
5 AND 7 AND 10 7.A
8 MHz 7.F
www.octoscope.com
24. 24
WiMAX Frequency Bands - FDD
Band (GHz)BW (MHZ) Duplexing Mode Duplexing Mode MS Transmit Band (MHz) BS Transmit Band Bandwidth
Class BS MS (MHz) Certification
Group Code
2 2.305-2.320, 2.345-2.360
2x3.5 AND 2x5 AND 2x10 FDD HFDD 2345-2360 2305-2320 2.E**
5 UL, 10 DL FDD HFDD 2345-2360 2305-2320 2.F**
3 2.496-2.690
2x5 AND 2x10 FDD HFDD 2496-2572 2614-2690 3.B
5 3.4-3.8
2x5 AND 2x7 AND 2x10 FDD HFDD 3400-3500 3500-3600 5.D
6 1.710-2.170 FDD
2x5 AND 2x10 FDD HFDD 1710-1770 2110-2170 6.A
2x5 AND 2x10 AND FDD HFDD 1920-1980 2110-2170 6.B
Optional 2x20 MHz
2x5 AND 2x10 MHz FDD HFDD 1710-1785 1805-1880 6.C
7 0.698-0.960
2x5 AND 2x10 FDD HFDD 776-787 746-757 7.B
2x5 FDD HFDD 788-793 AND 793-798 758-763 AND 763-768 7.C
2x10 FDD HFDD 788-798 758-768 7.D
5 AND 7 AND 10 (TDD), TDD or FDD Dual Mode TDD/H- 698-862 698-862 7.E*
2x5 AND 2x7 AND 2x10 (H-FDD) FDD
2x5 AND 2x10 MHz FDD HFDD 880-915 925-960 7.G
8 1.710-2.170 TDD
5 AND 10 TDD TDD 1785-1805, 1880-1920, 1785-1805, 1880-1920, 8.A
1910-1930, 2010-2025 1910-1930, 2010-2025
WiMAX Forum Mobile Certification Profile R1 5 v1.3.0 www.octoscope.com
25. 25
Summary
• LTE is here
Verizon and ATT
• Beyond commercial markets LTE is also being
embraced by
Military and Public Safety markets
Intelligent Transportation Systems
Possibly Smart Grid
• Carrier to carrier roaming remains to be seen
www.octoscope.com
26. 26
For More Information
• White papers, presentations, articles and test reports
on a variety of wireless topics
www.octoscope.com
www.octoscope.com
27. 27
LTE Resource Allocation
180 kHz, 12 subcarriers with normal CP
User 2 User 3 User 2 User 1 0.5 ms
User 2 User 3 User 2 User 1 7 symbols with normal CP
User 2 User 3 User 3 User 2
Time
User 2 User 1 User 3 User 2
User 1 User 1 User 3 User 1 Resource Block (RB)
Frequency
• Resources are allocated per user in time and frequency. RB is the basic unit
of allocation.
• RB is 180 kHz by 0.5 ms; typically 12 subcarriers by 7 OFDM symbols, but the
number of subcarriers and symbols can vary based on CP
CP = cyclic prefix, explained ahead www.octoscope.com
28. 28
Resource Block
A resource block (RB) is a basic unit of access allocation. RB bandwidth per slot (0.5
ms) is 12 subcarriers times 15 kHz/subcarrier equal to 180 kHz.
1 slot, 0.5 ms
…
Resource block 12
… subcarriers
Subcarrier (frequency)
…
Resource Element 1 subcarrier
1 subcarrier
QPSK: 2 bits
16 QAM: 4 bits v
64 QAM: 6 bits
…
Time
www.octoscope.com
29. 29
SC-FDMA vs. OFDMA
15 kHz subcarrier
Downlink – lower symbol rate
Uplink – higher symbol rate,
lower PAPR
S1 S2 S3 S4 S5 S6 S7 S8 …
60 kHz
Sequence of symbols Time
Frequency
www.octoscope.com
30. Intelligent Transportation Systems (ITS)
• Emerging market
• Embracing 802.11p
and LTE with 802.11p
sophisticated
LTE
software stacks on
top ITS
www.octoscope.com
31. 31
Voice over LTE Solutions
• CSFB (3GPP 23.272) whereby voice calls are switched
to 2G/3G CS networks
• VoLGA whereby voice calls are encapsulated in data
packets traversing LTE networks
• Over-the-Top (OTT) voice, for example Skype operating
over LTE networks
• GSMA’s selected Voice over LTE (VoLTE) based on IMS
CSFB = circuit switched fallback
CS = circuit switch
VoLGA = voice over LTE with Generic Access
OTT = over-the-top
VoLTE = voice over LTE
IMS = IP multimedia subsystem
www.octoscope.com
Hinweis der Redaktion
3GPP has defined EPS in Release 8 as a framework for an evolution or migration of the3GPP system to a higher-data-rate, lower-latency packet-optimized system that supports multiple radio-access technologies. The focus of this work is on the packet switcheddomain, with the assumption that the system will support all services—including voice—in this domain. (EPS was previously called System ArchitectureEvolution.)Although it will most likely be deployed in conjunction with LTE, EPS could also be deployed for use with HSPA+, where it could provide a stepping-stone to LTE. EPS willbe optimized for all services to be delivered via IP in a manner that is as efficient as possible—through minimization of latency within the system, for example. It will supportservice continuity across heterogeneous networks, which will be important for LTE operators that must simultaneously support GSM/GPRS/EDGE/UMTS/HSPA customers.One important performance aspect of EPS is a flatter architecture. For packet flow, EPS includes two network elements, called Evolved Node B (eNodeB) and the AccessGateway (AGW). The eNodeB (base station) integrates the functions traditionally performed by the radio-network controller, which previously was a separate nodecontrolling multiple Node Bs. Meanwhile, the AGW integrates the functions traditionally performed by the SGSN. The AGW has both control functions, handled through theMobile Management Entity (MME), and user plane (data communications) functions. The user plane functions consist of two elements: a serving gateway that addresses 3GPPmobility and terminates eNodeB connections, and a Packet Data Network (PDN) gateway that addresses service requirements and also terminates access by non-3GPP networks.The MME, serving gateway, and PDN gateways can be collocated in the same physicalnode or distributed, based on vendor implementations and deployment scenarios.The EPS architecture is similar to the HSPA One-Tunnel Architecture, discussed in the“HSPA+” section, which allows for easy integration of HSPA networks to the EPS. EPSalso allows integration of non-3GPP networks such as WiMAX.EPS will use IMS as a component. It will also manage QoS across the whole system,which will be essential for enabling a rich set of multimedia-based services.The MME, serving gateway, and PDN gateways can be collocated in the same physicalnode or distributed, based on vendor implementations and deployment scenarios.The EPS architecture is similar to the HSPA One-Tunnel Architecture, discussed in the“HSPA+” section, which allows for easy integration of HSPA networks to the EPS. EPSalso allows integration of non-3GPP networks such as WiMAX.EPS will use IMS as a component. It will also manage QoS across the whole system,which will be essential for enabling a rich set of multimedia-based services.Elements of the EPS architecture include:- Support for legacy GERAN and UTRAN networks connected via SGSN.- Support for new radio-access networks such as LTE.- The Serving Gateway that terminates the interface toward the 3GPP radio-accessnetworks.- The PDN gateway that controls IP data services, does routing, allocates IPaddresses, enforces policy, and provides access for non-3GPP access networks.- The MME that supports user equipment context and identity as well asauthenticates and authorizes users.- The Policy Control and Charging Rules Function (PCRF) that manages QoSaspects.
OFDM has proven to make the best use of the challenging wireless channel. The figure at the lower left shows that the quality of the wireless channel varies as a function of frequency and as a function of time. Even if I stand with my wireless device in one place, the signal at its receiver will fluctuate. The nulls in the signal are due to multipath and doppler fading. The wider the channel, the more difficult it is to equalize the received signal. OFDM takes a divide and conquer approach.OFDM transforms the frequency- and time-variable fading channel into multiple parallel correlated flat-fading channels. The narrow channels of each OFDM subcarrier exhibit small variations, making equalization simple. Thus, the OFDM channel can be arbitrarily wide. When OFDM is combined with multiple antenna techniques that we will discuss later, we can very effectively combat the time and frequency variability of the channel.
LTE uses a variety of multiple antenna techniques. Sometimes we loosely refer to these as MIMO (Multiple Input Multiple Output). MIMO enables spatial multiplexing whereby multiple streams of data (called layers in LTE) are transmitted in the same channel simultaneously. Spatial Multiplexing is only possible in a decorrelated channel and with multiple transmitters and receivers.In addition to Spatial Multiplexing, Multiple antenna techniques include transmit and receive diversity in MISO, SIMO and MIMO configurations. Spatial Multiplexing typically requires high signal to noise ratio (SNR) conditions. In the presence of low SNR or excessive doppler, multiple transmitters can be used for transmit diversity such as Cyclic Delay Diversity CDD and multiple receivers can be used for receive diversity techniques such ash MRC maximal ratio combining. Both transmit and receive diversity can be used simultaneously, further improving the robustness of the channel. While spatial multiplexing of 2 layers has the potential of doubling the data rate, diversity techniques use multiple radios for redundant transmission of a single stream and hence have lower theoretical throughout. LTE MIMO radios can dynamically select Spatial Multiplexing in channel conditions that are suitable for this and then switch to transmit and receive diversity when channel conditions deteriorate.
A MIMO device with multiple radios can implement transmit diversity in addition to receive diversity. Receive diversity on a MIMO device can also more sophisticated than on a single-radio device because the complete packet and not just preamble can be received by multiple receivers and then the receive source can be selected based on signal quality or by combining multiple received signals. This technique is known as maximal ratio combining (MRC).One can think of receive diversity as analogous to having two ears and transmit diversity as analogous to having two mouths. Transmit diversity techniques aim to produce multiple versions of the same signal and they are specifically designed to carefully control the relationship of these multiple versions of the signal so as to optimize signal reception.Transmit and receive diversity techniques can be used independently or together.When channel conditions allow, MIMO radios can also use spatial multiplexing whereby multiple radios are used to transmit more than one simultaneous data stream thereby multiplying the capacity of the airlink.
By having control over which subcarriers are assigned in which sectors, LTE can control frequency reuse. By using all the subcarriers in each sector, the system wouldoperate at a frequency reuse of 1; but by using a different one third of the subcarriers in each sector, the system achieves a looser frequency reuse of 1/3. The looser frequency reduces overall spectral efficiency but delivers high peak rates to users.
Most WCDMA and HSDPA deployments are based on FDD, where the operator uses different radio bands for transmit and receive. An alternate approach is TDD, in whichboth transmit and receive functions alternate in time on the same radio channel.Many data applications are asymmetric, with the downlink consuming more bandwidth than the uplink, especially for applications like Web browsing or multimedia downloads. A TDD radio interface can dynamically adjust the downlink-to-uplink ratio accordingly, hence balancing both forward-link and reverse-link capacity.TDD systems require network synchronization and careful coordination between operators or guard bands.
This table shows the FDD bands that are allocated in different regions of the world. The regions are shown in right column. FDD spectrum is paired spectrum, so for each channel we have the uplink band and the downlink band. The FDD frequency range spans from around 700 MHz to just under 2700 MHz.
The TDD bands are generally higher in frequency than the FDD channels. One reason for this is that TDD bands are more recent allocations. FDD bands have also been allocated for use by 3G. The TDD frequency range is from 1850 to 2620 MHz.
The multiple-access aspect of OFDMA comes from being able to assign different usersdifferent subcarriers over time. A minimum resource block that the system can assign toa user transmission consists of 12 subcarriers over 14 symbols (approx 1.0 msec.)