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Fourth Generation Cellular Systems: Spectrum Requirements. Joseph M. Nowack Member of the Technical Staff Communication Systems and Technologies Labs December 6, 2000. Higher bit rates. User services. White space. Wireless Internet. Service providers. Wireless wireline.

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Fourth Generation Cellular Systems: Spectrum Requirements

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fourth generation cellular systems spectrum requirements

Fourth Generation Cellular Systems:Spectrum Requirements

Joseph M. Nowack

Member of the Technical Staff

Communication Systems and Technologies Labs

December 6, 2000

what is 4g

Higher bit rates

User services

White space

Wireless Internet

Service providers

Wireless wireline

Technology trends

New air interface

New network

What is 4G?
  • The simple answer: 4G is the next major generation of mobile cellular systems, to be deployed around the year 2010
  • The multiple choice answer: The “twelve views” of 4G*

Higher bit rates

Cost reduction

Cost reduction

User services

White space

Wireless Internet

Strict generation

Is that your final answer?

Service providers

Wireless wireline

Technology trends

New air interface

4G will not exist

New network

*source: CSTL 4G white paper

a view of 4g
A View of 4G
  • Domain of 4G extends beyond 1G, 2G, and 3G
    • > 2 Mbps in a wide-area mobile system (> 20 Mbps peak)
  • Could coexist with 2G and 3G
  • 4G is not necessarily defined by the bit rate, but by a significant advance in system capability beyond what can be achieved with 3G





High Mobility



Limited Mobility




Milli-wave LAN


Fixed Access

Data Rate




some key challenges
Some Key Challenges
  • Coverage
    • Transmit power limitations and higher frequencies limit the achievable cell size
  • Capacity
    • Current air interfaces have limited peak data rate, capacity, and packet data capability
  • Spectrum
    • Location and availability are key issues
    • Lower carrier frequencies (< 5 GHz) are best for wide-area coverage and mobility
  • Carrier frequency has a larger impact on cell size than data rate
  • In order to enable wide-area coverage, 4G needs “mobile friendly” spectrum (ideally less than 5 GHz)
    • Mobile devices have low transmit power, limited antenna gain, and predominately non-line-of-sight propagation
  • Fixed wireless systems are more easily able to take advantage of higher carrier frequencies
    • No movement -> low Doppler
    • Higher transmit power
    • Power consumption/heat dissipation less critical
    • Line-of-sight more likely
    • High-gain, high-elevation antenna
broadband wireless content
Broadband Wireless Content
  • Successful wireless services are preceded by growth of wired demand

POTS  Mobile Telephony

Dial-up Internet  WAP, Cellular Data

DSL, Cable Data  4G Broadband Wireless

  • Content is rapidly expanding to serve the Cable/DSL connected consumer
    • Many sites focused on video delivery of “Broadband” video (typically 300 kbps and faster)
      • MovieFlix, VideoSeeker, QTV, Quokka Sports
  • Combinations of existing content may be valuable to mobile information consumers
    • Expressway Travel Information – real time web cameras, traffic status and advisories
    • Entertainment Selections – movie trailers, ticket reservation, TV guide, video-on-demand
    • Business Guide – Stock market information, real-time video briefings, breaking news
user session traffic characterization

Web browsing session (TCP)

Video Download (UDP)

Internet Telephony Audio – from Client

Internet Telephony Audio – to Client

User Session Traffic Characterization
typical observations
200-second sections of sessions using three applications

Packet data traffic rates are provided in bytes per second


average = 2059


Browsing the World Wide Web

( TCP & HTTP )

• Bursty data traffic

• Acquisition of various sources for a single site

• Long pauses by user

• TCP upstream packet traffic volume moderate

Peak-to-Average Bit Rate Ratio – 8.0

Ratio of Download Byte Volume

To Upstream – 8.8

Video + Audio Download

( UDP & VXtreme™ )


average = 5232


• UDP data uses fewer upstream packets than TCP

• Peak-to-Average data rate ratio low in this trace

• Mainly due to embedded constant bit rate

(CBR) audio stream of the downloaded sample

• Variable bit rates (VBR) are more common

for most video applications

Peak-to-Average Bit Rate Ratio – 1.37

Ratio of Download Byte Volume

To Upstream – 394.8

Typical Observations

Interactive Internet Telephony

( UDP & Internet Phone™ )


average = 1362


• Packet data rates reflect telephone speech patterns

• Remote participant responsible for more speech

and packet traffic than client in this trace

• Byte volumes generally comparable

Peak-to-Average Bit Rate Ratio – 1.85

Ratio of Download Byte Volume

To Upstream – 1.27

4g concept system
4G Concept System
  • A demonstration of broadband mobile systems in Schaumburg, Illinois
    • A one-directional broadband downlink carrier on DVB-T (WA9XHI)
    • A narrowband uplink via a cellular data connection (Sprint CDMA data)
  • Proving ground for asymmetric mobile broadband
  • Develop application understanding to apply to broadband air interface designs
  • Platform to demonstrate custom applications
  • Increasing levels of integration
    • Phase 1 – Vehicular mobility with a larger off-the-air receiver – May 2000
    • Phase 2 – Personal mobility with an integrated laptop receiver – Progressing


Internet Server

Proxy & Router



5-30 Mbps


Sprint PCS

4g system research areas


Antennas for



Air Interface




4G System Design

4G System Research Areas
4g air interface characteristics
4G Air Interface Characteristics
  • Higher bit rates than 3G (20 Mbps < peak < 200 Mbps)
  • Higher spectral efficiency and lower cost per bit than 3G
  • Air interface and MAC optimized for IP traffic (IPv6, QoS)
    • Adaptive modulation/coding with power control, hybrid ARQ
  • Smaller cells, on average, than 3G
    • However, cell size will be made as large as possible via:
      • Asymmetry - used to boost uplink range when necessary
      • Adaptive antennas (4 to 8 elements at base station, 2 elements at terminal)
  • Higher frequency band than 3G (below 5 GHz preferred)
  • RF channel bandwidths of 20-100 MHz
  • OFDM is promising (especially for downlink), but also investigating other methods
  • 4G still in a formative stage (commercial 2010)
  • Frequency bands less than 5 GHz preferred for wide-area, mobile services
  • 4G system bandwidth between 20 and 100 MHz (paired or unpaired)
  • ITU Working Group 8F beginning to consider the requirements and spectrum needs
  • International 4G spectrum harmonization