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II. Third Generation System Description(1)

Introduction

Third generation or IMT-2000 services are the names commonly used to refer to the next generation mobile wireless telecommunications services. The 3G family of services, and the systems that will provide them, are intended to reflect a high degree of commonality and are to be compatible with each other. These services will support mobile and fixed users employing a wide range of devices including small pocket terminals, handheld telephones, laptop computers, and fixed-receiver equipment. Third generation services are envisioned to be ubiquitous throughout the globe, as available in a remote part of a developing country as they are in an urban area in a highly developed country. Seamless roaming is a key attribute. Access to services is expected to be uniform. Furthermore, the user will be able to roam from an urban to a suburban and into a rural setting without loss of basic services.

The ITU has been fostering the development of the underlying radio and network standards for what is now defined as IMT-2000 services for over 15 years. The radio transmission technologies (RTTs) providing for standardized 3G air-interfaces adopted in November 1998 were the culmination of many years of arduous effort under the auspices of the ITU's Radiocommunication Sector (ITU-R) Task Group 8/1. These RTTs form the basis for connecting the user's mobile or portable device to the physical infrastructure supporting IMT-2000 services. ITU-R Task Group 8/1 also developed methods that can be used to assess the amount of additional spectrum needed to accommodate the expected future growth in demand for 3G mobile services.(2) The ITU's Telecommunication Standardization Sector (ITU-T) is actively working to develop 3G signaling and communication protocols, network requirements needed to support expected 3G services, and service definitions for IMT-2000 applications. Table 1 below, derived from ITU-T Draft Recommendation Q.1701,(3) describes selected essential capabilities of IMT-2000 systems.

Consumer demand for services available at any place, coupled with the expectation of high quality and increased transmission speed, are key drivers in the effort to establish commonality and compatibility of 3G terrestrial telecommunication systems. It is estimated that by the year 2010 there will be one billion wireless subscribers worldwide on 3G networks.(4) At the present time, the worldwide penetration of wireless service is approximately 7 percent and it is expected to exceed 30 percent by the end of the first decade of the new millennium.(5) There are over 1,300 cellular and second-generation terrestrial mobile service networks currently operating worldwide, each with a limited geographic coverage. It becomes more important to harmonize spectrum allocations for 3G services if companies are to provide uniform services and seamless roaming on a regional or global scale.

Table 1

IMT-2000 Services/Capabilities

Capabilities to support circuit and packet data at high bit rates:

- 144 kbs or higher in high mobility (vehicular) traffic

- 384 kbs or higher for pedestrian traffic

- 2 mbs or higher for indoor traffic

Interoperability and roaming among IMT-2000 family of systems
Common billing/user profiles:

- Sharing of usage/rate information between service providers

- Standardized call detail recording

- Standardized user profiles

Capability to determine geographic position of mobiles and report it to both the network and the mobile terminal
Support of multimedia services/capabilities:

- Fixed and variable rate bit traffic

- Bandwidth on demand

- Asymmetric data rates in the forward and reverse links

- Multimedia mail store and forward

- Broadband access up to 2 mbs

Spectrum Identified for IMT-2000

The ITU concluded that IMT-2000, or 3G, systems will require use of spectrum that extends beyond that already encumbered by first and second generation mobile systems. A major issue in the global debate regarding 3G system design, standards, and services that must be resolved is the amount of common or "harmonized" spectrum that will be available on a global and regional basis to support 3G systems. For ease in roaming, to help stimulate commonality in services and economies of scale, proponents of 3G services believe it is important to identify as much contiguous, harmonized spectrum to support worldwide 3G operations as is practical. This will stimulate the development of global and regional coverage of 3G systems by reducing the cost and complexity for system development, thus providing users with more cost-effective services.

Referring back to the data rates given in the first row in Table 1 above, and assuming state-of-the-art data compression capabilities, signal processing gains, and signal processor chip rates, the amount of channel bandwidth needed to provide wireless services at 2 mbs could be as much as 15-20 MHz (one-way); at 384 kbs it could be a high as 5 MHz (one-way). Current second-generation mobile systems easily support 9.6-14.4 kbs data rates using channel bandwidths of 30-200 kHz, with 64 kbs being possible when employing sophisticated channelization and coding schemes. The 25 to over 500-fold increase in channel bandwidth needed to provide higher-end data rates dramatically illustrates the reason for the demand for additional spectrum to support 3G wireless services.

WARC-92. At the 1992 World Administrative Radio Conference (WARC-92), 230 MHz of spectrum at 1885-2025 MHz and 2110-2200 MHz was identified for use by countries wishing to implement 3G systems. Shortly after WARC-92, the FCC conducted auctions for licenses in the paired 1850-1910/1930-1990 MHz band which lead to the rapid deployment of advanced mobile wireless communications services throughout the United States. The success of the PCS rollout has done much to increase competition in the provision of mobile telecommunications services in the United States and at the same time has stimulated the demand for even more advanced wireless services. Recently, countries around the world have started to license 3G systems within paired frequency bands identified at WARC-92: 1920-1980/2110-2170 MHz. The United Kingdom (UK) and Germany have, for example, conducted auctions for IMT-2000 spectrum within the past four months. The United States and the European experience indicates that the demand for advanced mobile services is projected to continue to grow at a rapid rate for some time to come.

WRC-2000. At the WRC-2000, additional spectrum to support IMT-2000 services was identified.(6) Three frequency bands, consistent with those proposed by the United States to the conference, were identified for use by administrations wishing to implement IMT-2000 services in addition to those adopted at WARC-92.

IMT-2000 System Characteristics. During preparations for WRC-2000, the United States committed to studying the feasibility of using the 1755-1850 MHz and 2500-2690 MHz bands (or parts thereof) for IMT-2000 operations. Such a study would involve determining the impact of the operation of IMT-2000 systems on the systems already licensed to operate in these bands. The 1755-1850 MHz band is used in the United States to support Government services, mostly military space operations, air-to-air training missions, and tactical communications operations. The 1755-1850 MHz band is also used by Federal law enforcement agencies to conduct covert video surveillance across the United States and Possessions (US&P) during criminal investigations and protective/security operations. The 1710-1755 MHz portion of the 1700/1800 MHz band identified at WRC-2000 is currently in the process of becoming available for commercial use. The 1850-1885 MHz portion of the same IMT-2000 band is already used to support PCS operations in the United States. The 2500-2690 MHz band is used to provide instructional television fixed services and multi-point distribution services throughout the United States.

Because of the physical processes governing the propagation of radio waves in the frequency range below 3 GHz, these frequencies can be efficiently transmitted and received by small, compact, relatively lightweight user terminals. This feature, coupled with the ability to support high data rates, makes them ideally suited for uses requiring mobility and portability of telecommunications services. Any 3G service that is targeted to mobile users is most effectively provided by taking advantage of the properties of radio waves operating below 3 GHz. Those 3G applications where the data rates are so high that fixed terminals are needed, or terminals that require antennas so large that they can only be employed in a stationary configuration, are better provided using frequencies above 3 GHz that can more effectively support higher data rate systems. It is the problem of identifying the spectrum bands that can and cannot be used to support 3G services that forms the crux of the effort to assess the degree to which IMT-2000 services can be included in bands already encumbered by services operating at 1755-1850 and 2500-2690 MHz.

In order to determine the impact of operating IMT-2000 systems in bands that are encumbered, it is necessary to assess to what degree the proposed and incumbent systems can co-exist in the same band. Stated in simple radio engineering terms, it is necessary to determine whether or not harmful interference is generated into one of the systems (incumbent or proposed) by the operation of the other(s). Furthermore, if it is determined that harmful interference is likely to occur, it is desirable to isolate the conditions under which it occurs and whether or not there exists means to mitigate its effects and costs associated with implementing such mitigation techniques.

The interference assessment mentioned above requires values of the technical characteristics for the systems being studied and the ability to quantify the systems' performance. For the case of the incumbent systems in the bands 1755-1850 MHz and 2500-2690 MHz, it is reasonable to assume that the pertinent parameters required for interference analysis studies are readily available to the individuals tasked with performing the studies. This is not the case however for all the parameters that are required to characterize IMT-2000 systems. These systems, many of which are in the planning or development stage, do not have well-defined or universally accepted values associated with every system parameter. Thus, we assume values for certain IMT-2000 system parameters that are to be used in the conduct of the interference studies. When assumptions had to be made concerning values to be used in characterizing IMT-2000 systems, an attempt was made to adopt values that are consistent with values documented in readily available material such as the reports and recommendations of the ITU-R, reports and findings of industry-led working groups addressing IMT-2000 issues, and absent any other readily available information, FCC rules for second-generation (PCS) mobile systems that were used as guides for 3G systems. In addition to values for the technical parameters themselves, it is also necessary to assume certain characteristics of the rollout of proposed IMT-2000 services, such as when they are likely to occur, whether there will be a time-phasing of the rollout, what regions of the globe are likely to support rollout earlier than others, and within a region, whether there will be a geographical preference i.e., urban versus suburban versus rural, for the rollout. These assumptions also were based on as readily available material and information as possible.

Tables 2 through 5 provide information on the various IMT-2000 system parameters and rollout characteristics that are to be used in undertaking the studies being addressed here.

Table 2

Characteristics of IMT-2000 Mobile Stations

Parameter CDMA-2000 CDMA-2000 UWC-136

(TDMA)

UWC-136

(TDMA)

W-CDMA
Carrier Spacing 1.25 MHz 3.75 MHz 30 kHz 200 kHz 5 MHz
Transmitter Power 100 mW 100 mW 100 mW 100 mW 100mW
Antenna Gain 0 dBi 0 dBi 0 dBi 0 dBi 0 dBi
Antenna Height 1.5 m 1.5 m 1.5 m 1.5 m 1.5 m
Body Loss 0 dB 0 dB 0 dB 0 dB 0 dBi

Access Techniques CDMA CDMA TDMA TDMA CDMA
Data Rates Supported 144 kbps 384 kbps 44 kbps 384 kbps 384 kbps
Modulation Type QPSK/BPSK QPSK/BPSK 4-DQPSK

8-PSK

GMSK

8-PSK

QPSK
-3 dB 1.1 MHz 3.3 MHzf 0.03 MHz 0.18 MHz 3 GPP
-20 dB 1.4 MHz 4.2 MHz 0.03 MHz 0.22 MHz TS25.101
-60 dB 1.5 MHz 4.5 MHz 0.04 MHz 0.24 MHz
Receiver Noise Figure 9 dB 9 dB 9 dB 9 dB 9 dB
Receiver Thermal Noise Level -113 dBma

-105 dBmb

-109 dBma

-100 dBmb

-121 dBma -113 dBma -109 dBm in

384 kbps

Receiver Bandwidth
-3 dB 1.10 MHz 3.30 MHz 0.03 MHz 0.18 MHz
-20 dB 1.6 MHz 4.7 MHz 0.04 MHz 0.25 MHz
-60 dB 3.7 MHz 11 MHz 0.09 MHz 0.58 MHz
Eb/No for Pe = 10-3 6.6 dB 6.6 dB 7.8 dB 8.4 dB 3.1 dB*
Receiver Sensitivityc -107 dBm -103 dBm -101 dBm -94 dBm -106 dBm
Interference Threshold 1d -119 dBm -115 dBm -127 dBm -119 dBm N/A
Interference Threshold 2e -104 dBm -100 dBm -111 dBm -103dBm N/A

a In bandwidth equal to data rate
b In receiver bandwidth
c For a 10-3 raw bit error rate, theoretical Eb/No
d Desired signal at sensitivity, I/N = -6 dB for a 10 percent loss in range
e Desired signal 10 dB above sensitivity, S/(I+N) for a 10-3 BER
f Shaded values were estimated.
* Assumes Eb/No for Pe = 10E-6 without diversity



Table 3
Characteristics of IMT-2000 Base Stations
Parameter CDMA-2000 CDMA-2000 UWC-136
(TDMA)
UWC-136
(TDMA)
(GSM)
GPRS/EDGE
W-CDMA
Operating Bandwidth 1.25 MHz 3.75 MHz 30 kHz 200 kHz 5 MHz
Transmitter Power 10 W 10 W 10 W 10 W 10 W
Antenna Gain 17 dBi per 120 deg. sector 17 dBi per 120 deg. sector 17 dBi per 120 deg. sector 17 dBi per 120 deg. sector 17 dBi per 120 deg. sector
Antenna Height 40 m 40 m 40 m 40 m 40 m
Tilt of Antenna 2.5 degs down 2.5 degs down 2.5 degs down 2.5 degs down 2.5 degs down
Access Techniques CDMA CDMA TDMA TDMA CDMA
Data Rates Supported 144 kbps 384 kbps 30 kbps

44 kbps

384 kbps
384 kbps
Modulation Type QPSK/BPSK QPSK/BPSK 4-DQPSK

8-PSK

GMSK

8-PSK

QPSK
Emission Bandwidth
-3 dB 1.1 MHz 3.3 MHzf 0.03 MHz 0.18 MHz 3 GPP
-20 dB 1.4 MHz 4.2 MHz 0.03 MHz 0.22 MHz TS25.104
-60 dB 1.5 MHz 4.5 MHz 0.04 MHz 0.24 MHz  
Receiver Noise Figure 5 dB 5 dB 5 dB 5 dB 5 dB
Receiver Thermal Noise Level -117 dBma

-109 dBmb

-113 dBma

-104 dBmb

-125 dBma -117 dBma -113 dBm in 384 kbps
Receiver Bandwidth
-3 dB 1.10 MHz 3.3 MHz 0.03 MHz 0.18 MHz  
-20 dB 1.6 MHz 4.7 MHz 0.04 MHz 0.25 MHz  
-60 dB 3.7 MHz 11 MHz 0.09 MHz 0.58 MHz  
Eb/No for Pe = 10-3 6.6 dB 6.6 dB 7.8 dB 8.4 dB 3.4 dB*
Receiver Sensitivityc -111 dBm -107 dBm -101 dBm -94 dBm -110 dBm
Interference Threshold 1d -123 dBm -119 dBm -131 dBm -123 dBm N/A
Interference Threshold 2e -108 dBm -104 dBm -115 dBm -107 dBm N/A
a In bandwidth equal to data rate
b In receiver bandwidth
c For a 10-3 raw bit error rate, theoretical Eb/No
d Desired signal at sensitivity, I/N = -6 dB for a 10 percent loss in range
e Desired signal 10 dB above sensitivity, S/(I+N) for a 10-3 BER
f Shaded values were estimated.
* Assumes Eb/No for Pe = 10E-6 without diversity


Table 4
IMT-2000 Traffic Model Characteristicsa
Parameter Value
Traffic Environments Rural
Vehicular
Pedestrian
In-building (central business district)
Maximum Data Rates Rural - 9.6 kbps
Vehicular - 144 kbps
Pedestrian - 384 kbps
In-building - 2 Mbps
Cell Size Rural - 10 km radius
Vehicular - 1000 m radius
Pedestrian - 315 m radius
In-building - 40 m radius
Users per cell during busy hour Rural - not significant
Vehicular - 4700
Pedestrian - 42300
In-building - 1275
Percent of total uplink traffic
>64 kbps during busy hour
Rural - not significant
Vehicular - 34%
Pedestrian - 30%
In-building - 28%
Percent of total downlink traffic
>64 kbps during busy hour
Rural - not significant
Vehicular - 78%
Pedestrian - 74%
In-building - 73%
Average number of users per cell per MHz during busy hour assuming frequency duplex operation Rural Not significant
Vehicular < 64 kbps - 16
> 64 kbps - 4
Pedestrian < 64 kbps - 150
> 64 kbps - 64
In-building < 64 kbps - 4
> 64 kbps - 2
a Values in the table are for a mature network.


Table 5
Rate of IMT-2000 Network Developmenta
Local Environment Calendar Year
2003 2006 2010
Urban 10% 50% 90%
Suburban 5% 30% 60%
Rural 0% 5% 10%
a For some interactions the potential for interference will be influenced by the degree to which IMT-2000 networks are built out. Tables 4 and 5 identify assumptions that will be used in the assessments with respect to the degree to which US IMT-2000 networks are developed following the granting of licenses. The levels of aggregate emissions for a fully mature IMT-2000 environment will be taken from ITU-R 687.2 or other reference material as appropriate.


Endnotes

1. This section was furnished by the Federal Communications Commission.

2. ITU-R Recommendation M. [IMT.SPEC], ITU-R Radiocommunication Assembly, Istanbul, Turkey, May 2000.

3. ITU-T Draft Recommendation Q.1701, Geneva.

4. United States Talking Points for WRC-2000 on IMT-2000 spectrum requirements.

5. Id.

6. Provisional Finals Acts of WRC 2000, 8 May-2 June 2000, Istanbul, Turkey, International Telecommunication Union.


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