Long Term HSPA Evolution meets ITU IMT-Advanced requirements - White paper
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White paper Long Term HSPA Evolution meets ITU IMT-Advanced requirements
Executive summary
The volume of mobile data traffic is The advancements to the HSPA
Contents increasing at an ever faster rate, technology currently being finalized in
2. Progress in consistently beating predictions and 3GPP Release 11 are made by
3GPP standards leading to growing demand for implementing several key features:
4. Overview of the network improvements. One of the
ITU IMT-Advanced ‘4G’ major contributors to increases in • 8 carrier aggregation, giving
Requirements and HSPA traffic is the exploding popularity of up to eight times faster data
smartphones. Another is the speeds compared to single
5. 3GPP Release-11 HSPA increasing use of a wide variety of carrier operation.
features bridging the gap applications, with frequent updates to • 4x4 MIMO in the downlink, roughly
to IMT-A and from applications such as social doubling peak data rates and
5. 8-Carrier HSDPA networking sites and health system capacity for devices with
5. 4x4 MIMO monitoring functions. four Rx antennas compared to
for HSDPA devices with two Rx antennas.
This appetite for data is driving further • Uplink beamforming, 2x2 MIMO and
6. Uplink Beamforming, advances in radio technology, with 64 QAM. Uplink improvements
MIMO and 64QAM HSPA continuing to be deployed in which increase the peak data rate,
8. HSPA+ Multiflow parallel with LTE to meet demand. user performance and cell capacity.
Many performance-boosting • Multiflow - increases downlink user
9. Long Term HSPA Evolution
innovations are being applied to the throughputs at the cell edge.
Performance and IMT-A
latest standard releases of both HSPA
11. Summary and LTE. Indeed, the evolution of These features improve HSPA radio
11. Abbreviations HSPA standards to meet the ITU technology considerably, allowing Long
IMT-Advanced ‘4G’ requirements1 Term HSPA Evolution to fulfill the IMT-
shows no signs of slowing. Advanced requirements set by the ITU.
1. ITU-R Report M.2134, Requirements related to technical
performance for IMT-Advanced radio interface(s).
Progress in
3GPP standards
Development of the Long Term HSPA New 3GPP Release 11 features such support. These enhancements arise
Evolution standard beyond Release 10 as 8-carrier HSDPA and 4x4 MIMO in from several features, including
has been rapid. The first work to select the downlink, as well as 64QAM Non-contiguous 4-carrier HSDPA
features to be included was carried out modulation and 2x2 MIMO in the allocation, 8-Carrier HSDPA, HSPA+
in December 2010. Just over a year uplink, contribute significantly to Multiflow, Uplink Closed Loop Transmit
later, the latest 3GPP RAN plenary the evolution of peak data rates in the Diversity (uplink beamforming) and
meeting was able to close core HSPA radio. Further Enhanced Cell_FACH. The
specification work on the first 3GPP schedule for these key features
completed items and formally set the As important as the peak data rates is shown in Figure 2.
goals for the final ones. Figure 1 shows are, Release 11 also enhances
how the 2010 vision of Nokia Siemens spectrum utilization, system capacity,
Networks is becoming a reality. cell edge performance and smartphone
2 Long Term HSPA Evolution meets ITU IMT-Advanced requirements
Release 11
Release 10 336 Mbps
Release 9
168 Mbps
40 MHz, 2x2 MIMO
Release 8
84 Mbps 20 MHz, 4x4 MIMO
Release 7
42 Mbps 20 MHz
Release 5 2x2 MIMO
28 Mbps 10 MHz
2x2 MIMO
14 Mbps 10 MHz
DOWNLINK
No MIMO
5 MHz Release 11
2x2 MIMO
5 MHz
Release 9
No MIMO 70 Mbps
Release 7
23 Mbps
Release 6
11.52 Mbps 10 MHz
64QAM
5.76 Mbps 10 MHz 2x2 MIMO
16QAM
UPLINK
5 MHz
16QAM
5 MHz
QPSK
Figure 1. HSPA peak data rate evolution with increased bandwidth and number of antennae.
2010 2011 2012
4Q 1Q 2Q 3Q 4Q 1Q 2Q 3Q 4Q
3GPP RAN
meeting
number #50 #51 #52 #53 #54 #55 #56 #57 #58
8-Carrier HSDPA
Uplink closed loop transmit diversity
Uplink MIMO study Uplink MIMO with 64 QAM
HSDPA Multiflow study HSDPA Multiflow
Downlink 4x4 MIMO
Non-contiguous 4-carrier HSDPA allocation
Further enhanced Cell_FACH state
Figure 2. 3GPP work plan for Release 11 HSPA features.
Long Term HSPA Evolution meets ITU IMT-Advanced requirements 3
Overview of the ITU IMT-Advanced
‘4G’ requirements and HSPA
The IMT-Advanced requirements for
IMT-A minimum HSPA prior to Rel-11 HSPA Rel-11
‘4G’ set by ITU can be broadly
requirement (Pre-Rel-11 state of the art) (Rel-11 improvement)
categorized in three groups:
Peak spectral 15.0 bits/s/Hz 8.6 bits/s/Hz 17.2 bits/s/Hz
1. Peak spectral efficiency efficiency, (2x2 MIMO + 64QAM) (4x4 MIMO)
requirements. Downlink
2. System performance requirements Peak spectral 6.75 bits/s/Hz 2.3 bits/s/Hz 6.9 bits/s/Hz
measured in average and cell efficiency, (16QAM) (2x2 MIMO + 64QAM)
edge spectral efficiency (discussed Uplink
in more detail on page 9). Spectrum Scalable bandwidth, Scalable up to 20 MHz Scalable up to 40 MHz
3. Other requirements, such as flexibility up to 40 MHz (4-carrier HSDPA) (8-carrier HSDPA)
spectrum flexibility, handover
interruption and system latency. Table 1: Peak spectral efficiency and bandwidth scalability requirements.
The first and the third group of
requirements are straightforward to
assess, as a particular system can be IMT-A minimum HSPA prior to Rel-11
easily evaluated against the requirement
requirements. The second group of
requirements aims to provide a more Control plane latency ≤ 100 ms 75 ms
practical assessment of how well a User plane latency ≤ 10 ms 8 ms
radio system performs in diverse Handover Intra-frequency ≤ 27.5 ms 0 ms
deployment environments. interruption Inter-frequency ≤ 40 ms 13 ms
Evaluating a radio system against Inter-band ≤ 60 ms 13 ms
these requirements will involve an Table 2: Latency and handover interruption requirements.
extensive simulation to determine
system performance.
Many, if not most, of the requirements
are already within the reach of the
HSPA radio technology, but peak
spectral efficiency and bandwidth
flexibility requirements listed in Table 1
can only be met with the new features
introduced with Release 11.
4 Long Term HSPA Evolution meets ITU IMT-Advanced requirements
3GPP release 11 HSPA features
bridging the gap to IMT-A
3GPP Release 11 brings many
new features, with those discussed
below helping to bridge the gap
1.0
between current capabilities and
the IMT-A requirements. 0.9
0.8
8-Carrier HSDPA
0.7
Dual Carrier (DC) HSDPA is a 3GPP
Release 8 feature commercially 0.6
deployed in a large number of markets. Mean packet call
0.5
However, it is limited to aggregating throughputs:
two adjacent 5 MHz radio carriers 0.4
• 1 carrier: 7.9 Mbps
• 4 carriers: 26.8 Mbps
within the same band. In Release 9, • 8 carriers: 42.8 Mbps
the DC-HSDPA operation is extended 0.3
to two 5 MHz carriers, each on a
0.2 1 carrier and 1 UE/sector
separate frequency band. Release 10
4 carriers and 4 UEs/sector
extends multicarrier functionality to 0.1 8 carriers and 8 UEs/sector
aggregate four carriers, while Release
11 extends this still further to eight 0
carriers. This leads to a peak data 0 10 20 30 40 50 60 70 80 90 100
rate of 336 Mbps with 2x2 MIMO and Average UE packet throughput (Mbps)
of 672 Mbps when combined with
4x4 MIMO. Release 11 also enables
aggregating non-adjacent carriers on Figure 3: Cumulative distribution probability of the average device packet throughput
for 1, 4 and 8 carriers at low offered load.
the same frequency band.
Aggregating multiple carriers brings The gains depend significantly on the
substantial benefits for the end user load in the system. If the load is high,
because any free resources across all then there will be fewer free resources
2-RX 2-TX
carriers can be used flexibly. When on the other carriers, which results in
antennas antennas
some carriers are under-utilized, lower gains.
because of the bursty nature of data,
they can be allocated in parallel to a From the perspective of the ITU IMT-
user device. Unlike static allocations Advanced requirements, the 8-Carrier
of each user to a particular carrier, HSDPA allows for aggregating 40 MHz
every 2 ms the user device can of spectrum, meeting the requirement 1-2 streams
transmit data using the carrier or for flexible system bandwidth support
carriers that are experiencing the best up to 40 MHz.
conditions, such as interference Figure 4: 2x2 MIMO in downlink.
and carrier frequency, to maximize 4x4 MIMO for HSDPA
system throughput.
A multi-antenna solution with 2x2
The gains can be seen in Figure 3, MIMO has already been deployed in
2-RX 2-TX 4-RX 4-TX
which shows the cumulative the downlink in commercial HSDPA antennas
antennas antennas antennas
distribution of the average user networks. The next step is to push
throughput and the mean packet call the multi-antenna transmission to 4x4
delay for macro cells with an average MIMO, which can double the peak
cell load of 1 Mbps. data rate and also improve the typical
cell capacity and user data rates.
1-2 streams 1-4 streams
Figure 5: 4x4 MIMO operation in downlink.
Long Term HSPA Evolution meets ITU IMT-Advanced requirements 5
Release 5
2100 MHz
2100 MHz
This can be seen in Figure 6, showing
2100 MHz
the average cell throughput. It can be
seen that adding Rx antennas gives 14
more benefits than adding Tx
13.05
antennas, while the maximum gain
2100 MHz
12
is achieved by using four transmit 11.66
and four receive antennas. In that 10
case the system will automatically 9.64
adapt the number of streams 4Rx
8 8.04
from a 4-transmit antenna with 2Rx
beamforming, to up to four parallel 7.09
6 1Rx
MIMO streams. 6.15
5.59
4 4.69
From the perspective of the ITU
IMT-Advanced requirements, the 4x4 3.42
Handovers
MIMO, when coupled with 64QAM
between 2
LTE and HSPA
modulation, reaches 17.2 bits/s/Hz
peak spectral efficiency, exceeding the 0
1Tx 2Tx 4Tx
IMT-A minimum requirement of
15 bits/s/Hz.
Uplink Beamforming, Figure 6: Average cell throughput (Mbps) with different number of Rx and Tx antennas.
MIMO and 64QAM
Beamforming allows uplink dual link budget, which translates into up to
4Rx 2Rx 1Rx
antenna transmission to provide 30% higher average uplink data rates
better data rate coverage and lower throughout the cell and up to 40%
OPEX
interference from neighboring cells. higher data rates at the cell edge.
It will also double the peak uplink
rate using dual stream transmission In another analogy to downlink MIMO,
and triple it when coupled with in very good channel conditions and
64QAM modulation. when a high received signal-to-noise
In an approach that is analogous to ratio is possible, the user equipment
the downlink MIMO, the mobile device may use dual stream MIMO
uses two transmit paths and antennas transmission with two orthogonal beam
to form a complex radio wave pattern patterns. This effectively doubles the
in the multiple base station receive raw bit rate on the physical layer and,
antennas. In favorable radio when moving from 16QAM to 64QAM
conditions, this yields over 2 dB in the modulation, the raw bit rate is tripled.
1-TX 2 or 4 RX 2-TX 2 or 4 RX
antenna antennas antennas antennas
1 stream: Beamforming
2 streams: MIMO
Figure 7: Single Tx antenna uplink. Figure 8: Dual Tx antenna uplink enabling
beamforming transmit diversity and MIMO.
6 Long Term HSPA Evolution meets ITU IMT-Advanced requirements
Release 5
2100 MHz
2100 MHz
2100 MHz
To achieve received signal-to-noise
ratios that are high enough to make
2100 MHz
dual stream transmission with 64QAM
possible over a significantly large area,
25.0%
four or even eight receiver antennas,
or a combination of both, may need ISD 1km
to be deployed. Yet again this is 20.0% ISD 2.8km
analogous to what happens in
the downlink. 15.0%
Dual antenna transmission in the 10.0%
uplink
Release 5 should be viewed as two
separate features. First, there is uplink
Handovers 5.0%
between
beamforming, which is possible and
LTE and
2100 HSPA
MHz
beneficial in most environments and 0.0%
which provides better uplink data rate 0.25 1 4 10
coverage. Second is the uplink dual User Equipment density (User Equipment/sector)
stream
2100 MHz MIMO, which is possible only in
more limited scenarios and doubles the
uplink peak rate. Figure 9: Gain in average user throughput from uplink beamforming.
2100 MHz
Introducing 64QAM modulation does
not require two transmit antennas, but
when aimingCAPEX
for the highest peak data
2100 MHz
rates, it needs to be coupled with 90.0%
uplink MIMO. OPEX
80.0% ISD 1km
ISD 2.8km
Figures 9 and 10 show the gains of 70.0%
beamforming on the average and cell
60.0%
edge throughput. It can be seen that
Throughput gain
gains of up to 20% and 80% 50.0%
respectively can be achieved.
40.0%
From the perspective of the ITU IMT- 30.0%
Advanced requirements, uplink
Handovers
20.0%
between
beamforming helps achieve the
LTE and HSPA 10.0%
average and cell edge performance
requirements. The uplink 2x2 MIMO 0.0%
together with 64QAM modulation, 0.25 1 4 10
User Equipment density (User Equipment/sector)
achieves 6.9 bits/s/Hz peak spectral
efficiency, exceeding the IMT-A
minimum requirement of 6.75 bits/s/Hz. Figure 10: Gain in cell edge user throughput from uplink beamforming.
CAPEX
OPEX
Long Term HSPA Evolution meets ITU IMT-Advanced requirements 7
HSPA+ Multiflow
Interference Signal Signal Signal
Another feature enabling a better use
of resources in cellular systems is
HSPA+ Multiflow, which is designed to
improve cell edge data rates. Multiflow
enables the transmission of data
from multiple cells to a user device Data stream 1 Data stream 2 Data stream 1
at the common cell edge, instead of
transmitting the data via a single cell
as in HSDPA today. This is illustrated
in Figure 11 and Figure 12 for dual cell
Multiflow operation.
Figure 11: Conventional single-cell HSDPA. Figure 12: HSPA+ Multiflow.
Each of the data flows in Multiflow
can be scheduled independently,
simplifying the concept and enabling
simple inter-site deployment
without the need for tight network
synchronization. The presence of two
10
HSDPA flows from two cells leads to
a doubling of the power available 9
no Multiflow
for the desired signal at the device, 8 Multiflow
which is used to increase the overall 7
user throughput. 6
5
To eliminate the inter-stream
4
interference, the terminal should have +40%
3
two receive antennas and interference-
aware receiver chains. For 3GPP 2
Release 11, Multiflow is considered 1
for up to four different flows over two 0
different frequencies, enabling the Cell edge Average
radio network to send data from two
different base stations and up to four
different cells to a user device.
Figure 13: Cell edge and average user throughput with and without Multiflow.
Figure 13 shows the cell edge and
average user throughput with and
without Multiflow. It can be seen
that users at the cell edge particularly
benefit from Multiflow, since they
are the most likely to receive
transmissions from multiple cells
with adequate signal quality.
From the perspective of the ITU
IMT-Advanced requirements, HSPA+
Multiflow helps achieve the required
performance at the cell edge.
8 Long Term HSPA Evolution meets ITU IMT-Advanced requirementsLong term HSPA evolution
performance and IMT-A
The ITU IMT-Advanced evaluation The system performance requirements 2. ITU-R Report M.2135, Guidelines for evaluation
of radio interface technologies for IMT-Advanced.
guideline document2 details four for a candidate IMT-Advanced radio
different deployment environments and technology are shown in Table 4. The
sets performance criteria in each. evaluation criteria state that it is sufficient
Key parameters of the deployment to meet each requirement type in three
environments are described in Table 3. out of four deployment scenarios to
qualify as an IMT-Advanced radio.
Indoor hotspot Urban micro Urban macro Rural macro
InH UMi UMa RMa
BS-to-BS distance 60 m 200 m 500 m 1732 m
BS antenna elements Up to 8 Rx and 8 Tx
Total cell Tx power 21 dBm / 20 MHz 41 dBm / 10 MHz 46 dBm / 10 MHz 46 dBm / 10 MHz
BS antenna height 6 m, ceiling mounted 10 m, below rooftop 25 m, above rooftop 35 m, above rooftop
BS antenna gain 0 dBi 17 dBi 17 dBi 17 dBi
Device antenna elements Up to 2 Rx and 2 Tx
Device Tx power 21 dBm 24 dBm 24 dBm 24 dBm
Device speed 3 km/h (10 km/h) 3 km/h (30 km/h) 30 km/h (120 km/h) 120 km/h (350 km/h)
(high speed)
Carrier frequency 3.4 GHz 2.5 GHz 2.0 GHz 800 MHz
Table 3: Key deployment scenario parameters for the system performance evaluation.
Indoor hotspot Urban micro Urban macro Rural macro
InH UMi UMa RMa
Downlink average 3.0 bits/s/Hz 2.6 bits/s/Hz 2.2 bits/s/Hz 1.1 bits/s/Hz
spectral efficiency
Downlink cell edge 0.1 bits/s/Hz 0.075 bits/s/Hz 0.06 bits/s/Hz 0.04 bits/s/Hz
spectral efficiency
Uplink average 2.25 bits/s/Hz 1.8 bits/s/Hz 1.4 bits/s/Hz 0.7 bits/s/Hz
spectral efficiency
Uplink cell edge 0.07 bits/s/Hz 0.05 bits/s/Hz 0.03 bits/s/Hz 0.015 bits/s/Hz
spectral efficiency
High speed 1.0 bits/s/Hz 0.75 bits/s/Hz 0.55 bits/s/Hz 0.25 bits/s/Hz
spectral efficiency
VoIP capacity 50 users / MHz 40 users / MHz 40 users / MHz 30 users / MHz
Table 4: IMT-Advanced system performance requirements.
Long Term HSPA Evolution meets ITU IMT-Advanced requirements 9The evaluation of Long Term HSPA As shown, Long Term HSPA Evolution
Evolution performance against these meets all the IMT-Advanced
requirements was both a major performance requirements. The results
simulator development effort and a were obtained without using certain
long-lasting simulation campaign. The cell-edge performance enhancing
following figures show the simulation features such as scenario-optimized
results against the ITU IMT-Advanced scheduler or HSPA+ Multiflow, but
set requirements. assume a fairly advanced interference
suppressing receiver in the device.
4.5 0.18
4.0 DL Performance 0.16 DL Performance
UL Performance UL Performance
3.5 DL Requirement 0.14 DL Requirement
UL Requirement UL Requirement
3.0 0.12
2.5 0.10
2.0 0.08
1.5 0.06
1.0 0.04
0.5 0.02
0 0
InH UMi UMa RMa InH UMi UMa RMa
Figure 14: LTHE cell average spectral efficiency vs. IMT-A requirement Figure 15: LTHE cell edge user spectral efficiency vs. IMT-A requirement
in bits/s/Hz. in bits/s/Hz.
6 3.0%
4 Achieved voice outage
2.5% Maximum outage
2 requirement
0 2.0%
Safety Achieved C/I
margin
-2 Maximum C/I
1.5%
requirement
-4
-6 1.0%
Safety
-8 margin
0.5%
-10
-12 0.0%
InH @ UMi @ UMa @ RMa @ InH @ UMi @ UMa @ RMa @
10 km/h, 30 km/h, 120 km/h, 350 km/h, 250 users 200 users 200 users 150 users
1.0 bps/Hz 0.75 bps/Hz 0.55 bps/Hz 0.25 bps/Hz
Figure 16: LTHE high speed mobility traffic channel performance vs. Figure 17: LTHE voice outage performance vs. IMT-A requirement.
IMT-A requirement.
10 Long Term HSPA Evolution meets ITU IMT-Advanced requirementsSummary
To meet the increased network capacity • 8 carrier aggregation, giving up to In addition, a number of other
demand caused by growing mobile data eight times better user features, such as further
traffic, HSPA continues to be improved in performance. enhancements to Cell_FACH,
parallel with LTE. HSPA is currently the • 4x4 MIMO in the downlink, improve other aspects of
radio access technology serving the most increasing peak data rates and the system.
wireless broadband users worldwide and improving system performance.
the load on the system is expected to • Uplink beamforming, 2x2 MIMO These features deliver considerable
increase greatly in the coming years. and 64 QAM. Uplink improvements improvements to HSPA radio
increase the peak data rate, user technology, and as shown in this
HSPA Release 11 raises the performance performance and cell capacity. paper, Long Term HSPA Evolution
of HSPA systems significantly by offering • Multiflow - increases downlink user can fulfill IMT-Advanced
the following features: throughputs at the cell edge. requirements set by the ITU.
Abbreviations
3GPP Third Generation Partnership Project
CL-BFTD Closed Loop Beamforming Transmit Diversity
HSPA High Speed Packet Access
HSDPA High Speed Downlink Packet Access
IMT International Mobile Telecommunications
IMT-A IMT Advanced
IP Internet Protocol
ISD Inter-Site Distance
ITU International Telecommunication Union
ITU-R ITU Radio Communication Sector
LTE Long Term Evolution
LTHE Long Term HSPA Evolution
MIMO Multiple Input Multiple Output
QAM Quadrature Amplitude Modulation
UE User Equipment
VoIP Voice Over IP
Long Term HSPA Evolution meets ITU IMT-Advanced requirements 11Nokia Siemens Networks Corporation P.O. Box.1 FI-020022 NOKIA SIEMENS NETWORKS Finland Visiting address Karaportti 3, ESPOO, Finland Switchboard +358 71 400 4000 Product code: C401-00755-WP-201203-1-EN Copyright © 2012 Nokia Siemens Networks. All rights reserved. A license is hereby granted to download and print a copy of this document for personal use only. No other license to any other intellectual property rights is granted herein. Unless expressly permitted herein, reproduction, transfer, distribution or storage of part or all of the contents in any form without the prior written permission of Nokia Siemens Networks is prohibited. The content of this document is provided “AS IS”, without warranties of any kind with regards its accuracy or reliability, and specifically excluding all implied warranties, for example of merchantability, fitness for purpose, title and non-infringement. In no event shall Nokia Siemens Networks be liable for any special, indirect or consequential damages, or any damages whatsoever resulting form loss of use, data or profits, arising out of or in connection with the use of the document. Nokia Siemens Networks reserves the right to revise the document or withdraw it at any time without prior notice. Nokia is a registered trademark of Nokia Corporation, Siemens is a registered trademark of Siemens AG. The wave logo is a trademark of Nokia Siemens Networks Oy. Other company and product names mentioned in this document may be trademarks of their respective owners, and they are mentioned for identification purposes only. www.nokiasiemensnetworks.com
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