View stunning SlideShares in full-screen with the new iOS app!Introducing SlideShare for AndroidExplore all your favorite topics in the SlideShare appGet the SlideShare app to Save for Later — even offline
View stunning SlideShares in full-screen with the new Android app!View stunning SlideShares in full-screen with the new iOS app!
force the development to move from evolution
to revolution. The key trends include:
• Voice services will also stay important in fore-
seeable future, which means that capacity
optimization for voice services will continue. Vehicular
• Together with increasing use of IP-based appli-
cations, the importance of data as well as
simultaneous voice and data will increase.
• Increased need for data means that efficiency
of data services needs to be improved as well
as delay, and average and peak user data rates.
• When more and more attractive multimedia
terminals emerge in the markets, the usage of
such terminals will spread from office, homes,
and airports to roads, and finally everywhere. Pedestrian
This means that high-quality high-data-rate
applications will be needed everywhere.
• When the volume of data increases, the cost W
per transmitted bit needs to decrease in order lea M
to make new services and applications afford- 5 WLAN
able for everybody. Stationary
The data rate trends are summarized in Fig.
1. The other current trend in Fig. 1 indicates
0.1 1 10 100
that in the 3G evolution path very high data
rates are achieved in hot spots with WLAN Data rate (Mb/s)
rather than cellular-based standards.
I Figure 1. Data rate trends.
WCDMA EVOLUTION ANSWERS TO
EXPECTED TRENDS cells may be members of the active set, only one
The WCDMA evolution view from release 99 and transmits at any time [2, 3].
release 4 (March 2001) to beyond 3G can be seen As a result the peak data rate of HS-DSCH
in three phases. The three phases are described in will be about 10 Mb/s; based on preliminary simu-
detail below. In Third Generation Project Part- lation results the throughput of a cell/sector will
nership (3GPP) standardization phase 1 is already be roughly doubled when compared to release 99.
in progress; the other two phases try to highlight It is anticipated that not all of the proposed tech-
future potentials, but such development has yet to nical enhancements will be standardized in phase
be seen in 3GPP standardization. 1 (i.e., release 5). Release 5 will include some
very basic solutions like AMC and FHARQ.
Phase 1: High-Speed Downlink Packet Access — In the Also, from the time-division duplex (TDD)
first phase, the peak data rate and throughput of development viewpoint, high data rates can be
WCDMA downlink for best effort data will be seen as a necessity. Especially when we think
greatly enhanced when compared to release 99. about usage of TDD in the office environment,
In March 2000, a feasibility study on high-speed being competitive with frequency-division duplex
downlink packet access (HSDPA) was approved (FDD) mode and other indoor solutions is cru-
by 3GPP . The study report was released as cial. Thus, HSDPA for TDD mode in release 5
part of release 4, and the specification phase of will include some basic technical improvements.
HSDPA was completed in release 5 at the end Among the interesting research topics are
of 2001 . multiple-input multiple-output (MIMO) diversity
The feasibility study focused on defining a techniques, which are also studied as part of
high-speed downlink shared channel (HS-DSCH) HSDPA [2, 5]. They can potentially improve sys-
that inherits many of the features of the DSCH tem performance quite considerably, as shown in
defined in release 99. The main proposed techni- Fig. 2, which depicts the channel capacity based
cal enhancements of HS-DSCH include : on  for different Tx/Rx antenna configura-
• Adaptive modulation and coding (AMC) tions. Due to implementation complexity they
• Fast hybrid automatic repeat request (FHARQ) may become reality a little bit later than the
• Fast cell selection (FCS) other techniques proposed for HS-DSCH.
AMC is a radio link adaptation technique Therefore, from a timing perspective, MIMO
where the modulation order and channel coding techniques could be more relevant for phase 2
method are varied according to the quality of or 3 of WCDMA evolution.
the received signal [2, 3]. AMC is somewhat sen- Although HSDPA is raised here, 3GPP release
sitive to measurement errors and delays; there- 5 work includes and will include many other work
fore, FHARQ has been proposed to provide items that contribute to 3G development.
implicit link adaptation to instantaneous channel
conditions [2–4]. Phase 2: Uplink High-Speed Data, High-Speed Access for
FCS has also been proposed to potentially TDD — Although the main emphasis in air inter-
decrease interference and increase the capacity face optimization can be seen in the area of
of the system. Using FCS, the mobile terminal downlink high-data-rate support, the uplink also
indicates the best cell to serve it on the downlink needs attention. Enhanced data rates in the
through uplink signaling. Thus, while multiple uplink will benefit the end user (e.g., in file
IEEE Wireless Communications • April 2002 15
standards (IEEE 802.11a and HIPERLAN/2), will
30 offer bandwidths up to 54 Mb/s [7, 8].
In the past, WLANs have been mostly used
as a wireless replacement for wired LANs in the
25 office environment.
Recently, mobile business professionals have
increasingly been looking for an efficient way to
20 access corporate information systems and
databases remotely through the Internet back-
2 8 bone. However, the high bandwidth demands of
8 2 2 4
15 typical office applications (e.g., large email
attachment downloading) often calls for very fast
2 2 transmission capacity. Furthermore, certain hot
10 spots like airports and railway stations are natu-
ral places to use the services. However, in these
1 2 places the time available for information down-
5 load is typically fairly limited.
1 1 In light of the above there is a clear need for
a public wireless access solution that could cover
0 the demand for data-intensive applications and
0 5 10 15 20 25 enable smooth online access to corporate data
services in hot spots.
Together with high-data-rate cellular access,
I Figure 2. Channel capacity vs. number of antennas. WLAN has the potential to fulfill end user
demands in hot spot environments. WLAN offers
an interesting possibility for cellular operators to
transmission or when such office applications as offer additional capacity and higher bandwidths
NetMeeting are used). Also, an optimized uplink for end users without sacrificing the capacity of
can be designed to support lower terminal out- cellular users, since WLANs operate on unli-
put powers. censed frequency bands. Furthermore, solutions
Additionally, in phase 2 further improve- exist that enable operators to utilize the existing
ments of HSDPA for both FDD and TDD cellular infrastructure investments and well estab-
modes will be seen. This could include the above lished roaming agreements for WLAN network
mentioned FCS and MIMO techniques if subscriber management and billing.
proven, performance and implementation points The TDD component of the Universal Mobile
of view, feasible and useful. Telecommunications System (UMTS) Terrestrial
Radio Access Network (UTRAN) is also opti-
Phase 3: Capacity Improvements in Uplink and Downlink, mized for hot spot usage on unpaired TDD bands.
and Further Data Rate Enhancement — Some of the On one hand, the achievable end user data rates
foreseen air interface technologies become are lower than in WLAN systems; on the other
mature in a timeframe that may be unacceptable hand, the achievable cell sizes are larger. In addi-
for the proposed phases 1 and 2 of WCDMA tion, the cost savings in dual mode between
development. It is obvious, however, that further WCDMA FDD and TDD are significant, and may
enhancement will be introduced in later phases. support implementation of TDD in areas where
As the demand for very high data rates grows, dual mode with WCDMA is seen as essential.
we can expect the need to further enhance
WCDMA data rates up to significantly above 10 DEVELOPMENT IN ITU
Mb/s. Increase of spreading bandwidth in new
frequency allocations could be one answer to the Also, the International Telecommunication
technology challenge. Union (ITU) is working on systems beyond 3G.
So far the work has concentrated on looking at
Standardization Timeframe — Phase 1 of WCDMA the objectives for “beyond 3G systems.” One
evolution was completed in 2001. important aspect is that new spectrum is also
For later phases no approved workplan exist. needed before beyond 3G systems can be fully
The approximate schedule for phase 2 could deployed. This development is covered in .
align with following phases of 3GPP releases
(e.g., mid-2003 could be the right timeframe). BEYOND 3G: 4G
Phase 3 could again take place a couple of
years after phase 2, depending on market As mentioned earlier, services, applications, and
demand and spectrum availability. even the core network are evolving at high speeds,
and distinguishing different generations is not
OTHER TRENDS really possible anymore. The evolution, and some-
times revolution, is a very significant trend, but in
The other major trend is the development of this article 4G is seen as a revolution of the air
picocell and personal area network technologies interface rather than a new phase of evolution.
(e.g., WLAN and Bluetooth) for office, public, The other major trend is that access methods will
and home indoor solutions. be less tightly coupled to the network. This also
Current WLAN products are able to provide confuses generational thinking (Fig. 4).
bandwidths up to 11 Mb/s. The next-generation After a certain point, evolution is not no longer
wireless LAN products, based on recently approved an answer to air interface development, and revo-
16 IEEE Wireless Communications • April 2002
Evolution of 3G
Wide area coverage
GSM (MAP) GPRS EDGE EDGE Ph.2
15.2 kb/s 170 kb/s 473 kb/s 473 kb/s
30 kHz Real-time IP
TDMA (IS-41) Future
CDPD 5 MHz WCDMA TDD 2 Mb/s wireless
43.2 kb/s High-speed
WCDMA WCDMA downlink
FDD HSPA packet access
PDC/PDC-P 10 Mb/s
14.4 kb/s T-SCDMA
cdmaOne cdma2000- 1XEV - DO, phase 2.4 Mb/s
(IS-41) 1X 1XEV - DV, phase 5.4 Mb/s
76.8 kb/s 307. kb/s
WLAN 54 Mb/s HL2-
802.11b IEEE 802.11a
IEEE 802.11a standard
2000 2001 2002 2003 2010->
I Figure 3. The path toward 4G from a radio perspective. The time axis shows the estimated launch times of the actual systems.
lutionary concepts must also be considered. Fig-
ure 3 illustrates the evolution of 2G/3G cellular
and WLAN standards and the revolutionary step LAN
toward future wireless systems. GSM evolution
will continue in parallel with WCDMA. In the WLAN
United States, cdma2000-1X will be followed by Intranet Bluetooth
1XeV-DO (high-bit-rate data only) and 1XeV-
DV (high-bit-rate data and voice) standards. xDSL
Looking at development in the Internet and
applications, it is clear that the complexity of the ISDN
transferred content is rapidly increasing and will Internet POTS
increase further in the future. Generally it can
be said that the more bandwidth is available, the TDMA
more bandwidth applications will consume.
In order to justify the need for a new air GSM
interface, targets need to be set high enough to GPRS
ensure that the system will be able to serve us 2G/3G
long into the future. A reasonable approach CDMA
would be to aim at 100 Mb/s full-mobility wide
area coverage and 1 Gb/s low-mobility local area
coverage with a next-generation cellular system
in about 2010 in standards fora. Also, the future I Figure 4. Coupling of air interface technologies to the network.
application and service requirements will bring
new requirements to the air interface and new
emphasis on air interface design. One such issue, The demand for even higher data rates and
which already strongly impacts 3G evolution, is potential need for wider bandwidths in cellular
the need to support IP and IP-based multimedia. evolution raise even further questions on spec-
If both technology and spectrum to meet such trum needs. However, before this need can be
requirements cannot be found, the whole discus- defined, a much better idea/vision of the next
sion of 4G may become obsolete. generation will be needed. For example, if WLAN
is combined with WCDMA, the additional spec-
SPECTRUM ISSUES trum is already the current WLAN spectrum, and
something more is needed to justify even higher
WRC2000 already identified new spectrum for spectrum requirements. There are many discus-
IMT-2000 systems. The ITU identifications at 2 sions ongoing, for example, about reallocating
GHz frequency range can be seen in Fig. 5. In addi- analog TV bands for mobile systems. On the
tion to 2 GHz identifications, WRC2000 also iden- other hand, administrations seem to prefer more
tified parts of the 806–960 MHz band that already flexible air interfaces where globally harmonized
have primary mobile allocations to IMT-2000. spectrum would not be needed.
IEEE Wireless Communications • April 2002 17
 G. J. Foschini and M. J. Gans, “On Limits of Wireless
Communication in a Fading Environment when Using
Multiple Antennas,” Wireless Pers. Commun., vol. 6,
no. 3, Mar. 1998, pp. 311–35.
 E. Telatar, “Capacity of Multi-Antenna Gaussian Chan-
S5AAA S5388 S5388 S5AAA nels, Technical Memorandum,” Bell Labs, Lucent, Oct.
1995, published in Euro. Trans. Telecommun., vol. 10,
no. 6, Nov/Dec 1999, pp. 585–95.
 ETSI, “Broadband Radio Access Networks (BRAN); High Per-
1700 1750 1800 1850 1900 1950 2000 2050 2100 2150 2200 2500 2550 2600 2650 MHz formance Radio Local Area Network (HIPERLAN) Type 2;
Requirements and Architectures for Wireless Broadband
Access,” TR 101 031 (1999-01), v. 1.1.1. ETSI, 1999.
I Figure 5. ITU spectrum identification: S5.388 are the WARC ’92 identifica-  ETSI, “Broadband Radio Access Networks (BRAN); High
Performance Radio Local Area Network (HIPERLAN)
tions, and S5.AAA are the additional WRC 2000 identifications. Type 2. ETSI Technical Specification, Physical Layer,”
 D. McFarlane, “Enhancing the Capabilities of 3G Sys-
CONCLUSIONS tems,” IEEE Int’l. Conf. 3G Wireless and Beyond, 30
May–2 June, 2001, San Francisco, CA.
The WCDMA air interface is seen to develop
far beyond its initial capabilities to satisfy future BIOGRAPHIES
service and application needs. HARRI HONKASALO received his M.S. from Helsinki University of
WLAN systems are seen to complement Technology in 1986. In 1985 he joined Nokia. From 1985 to
1993 he held various research and product development
WCDMA-based cellular evolution in hot spots positions in Nokia Mobile Phones in Finland and the United
in development beyond 3G. The other technolo- Kingdom, working on GSM and PDC terminals and standard-
gy to be considered for hot spot coverage is ization. In 1994–1995 he was with Nokia Research Center in
UTRAN TDD mode, which is well harmonized Finland, responsible for research activities on GSM stan-
dards, and in 1996–1997 he was with Nokia Research Center
with WCDMA FDD and in such a way facili- in the United States, responsible for research activities on IS-
tates cost-efficient dual mode terminal design. 95 and cdma2000 standards. From 1998 to 2000 he was
When looking at development of services, head of system research in Nokia Mobile Phones with global
applications, or core networks, development responsibility for system research activities. Since 2001 he
has been director of IPR for Nokia Corporation with global
especially in applications is much faster than tra- responsibility for standards-related IPR activities. He has pub-
ditional generation thinking assumes. This devel- lished about 10 papers in international conferences and
opment will happen in an evolutionary way journals, and holds 13 patent families covering different
without clear generations. That is why here we areas of radio interfaces.
consider quantum leaps in air interface develop- KARI PEHKONEN [M] (email@example.com) received his
ment as different generations. The next such M.S., licentiate in technology, and doctor of technology
quantum leap will lead us to 4G. This thinking is degrees from the University of Oulu in 1987, 1989, and
well in line with development from 1G to 2G 1993, respectively. He joined the Computer Technology
Laboratory of the Technical Research Centre of Finland in
and 3G. People clearly refer to air interface 1987 and was involved in research on parallel program-
standards when referring to these generations. ming and parallel computers. During 1989–1990 he was a
4G needs to be something that 3G evolution visiting researcher at the Computer Vision Laboratory of
cannot do. Looking at the complexity of applica- the Center for Automation Research of the University of
Maryland, doing research on computer vision algorithms.
tion contents and development of such contents, Upon returning to Finland he continued with the Technical
going toward even higher data rates and avail- Research Centre, studying further the algorithms developed
ability of high data rates everywhere is a trend. during his visit to the United States. Since 1993 he has
Thus, one distinguishing factor between 3G and been with Nokia Mobile Phones, first as a research engi-
neer and then holding various managerial positions within
4G will be the data rates. We assume that 4G the company, doing research on WCDMA systems and
should support at least 100 Mb/s peak rates in standardization. From 1998to 2001 he was with Nokia
full-mobility wide area coverage and 1 Gb/s in Japan, responsible for ARIB standardization activities. Since
low-mobility local area coverage. There will be the beginning of 2001 he has been head of system research
at Nokia Mobile Phones with global responsibility for sys-
other characteristics for 4G, but at this point in tem research activities. He has published about 20 papers
time the requirements for 4G need further stud- in international conferences and journals and holds 9
ies (including market studies). patents covering different areas of radio interfaces. His cur-
rent research interests include the system aspects of radio
ACKNOWLEDGMENTS access networks with a special interest in L1 solutions.
This article is based on previously published ANNE-TUULIA LEINO received her M.S. degree from the Uni-
material from 3Gwireless 2001 organized by Del- versity of Technology, Espoo, in 1991. She joined the
son Group (http://www.delson.org). Telecommunications Administration Centre, Finland, in
1991, working on spectrum topics related to the regulation
of public mobile networks. She changed to Nokia Networks
REFERENCES in 1997 to work as a spectrum expert covering frequency
 Motorola, Work Item Description sheet for High Speed arrangements related to IMT-2000 networks.
Downlink Packet Access,” TSGR#7(00)0032, March
13–15, 2000, Madrid, Spain, p. 3. MARKKU NIEMI received his M.S. degree from Tampere Uni-
 3GPP TSG-RAN WG2, “UTRAN High Speed Downlink versity of Technology in 1995. He joined Nokia Mobile
Packet Access (release 4),” TSG-R2 TR 25.950. Phones in 1995 and currently is senior manager at Nokia
 “Nokia, Considerations on High-Speed Downlink Packet Mobile Phones responsible for WLAN standardization, reg-
Access (HSDPA),” TSGR1#14(00)0868, July 4–7, 2000, ulatory matters, and research cooperation. Prior to his cur-
Oulu, Finland, p. 9. rent position he held various management positions inside
 Nokia, Text proposal on HARQ for HSDPA TR, Nokia Mobile Phones. He has published about 10 papers in
TSGR1#17(00)1369, 21–24, Nov., 2000, Stockholm, international conferences and journals, and holds several
Sweden, p. 4. patent applications.
18 IEEE Wireless Communications • April 2002