Transcript 4th Generation Mobile Broadband Wireless Systems

Fourth Generation Cellular Systems:
Spectrum Requirements
Joseph M. Nowack
Member of the Technical Staff
Communication Systems and Technologies Labs
December 6, 2000
1
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
Higher
bit
bitrates
rates
Cost
Cost
reductio
reduction
n
User
User
services
services
White
space
Strict
generatio
n
Wireless
Internet
Is that your final
answer?
Service
provider
s
Wireless
wireline
Technolog
y trends
New
network
*source:
New air
interface
CSTL 4G white paper
4G will
not exist
2
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
Coverage
Area,
Mobility
Macrocell,
High Mobility
Microcell,
Limited Mobility
2G
3G
4G
WLA
N
Fixed Access
P-MP (LMDS)
Milli-wave LAN
Data Rate
64kbps
2Mbps
200Mbps
3
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
4
The Coverage Problem - Carrier Frequency and Data Rate
Increase in the number of cells needed to cover a fixed
geographic area due to an increase in either the system
data rate or carrier frequency.
1000
Carrier Frequency
100
Assumptions: Constant EIRP, constant Rx
antenna gain, no change in diffraction,
absorption or other propagation
characteristics. Path loss exponent = 4
Data Rate
10
1
1
10
100
1000
Data Rate or Carrier Frequency Increase Factor
5
Spectrum
• 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
6
Broadband Wireless Content
•
•
Successful wireless services are preceded by growth of wired demand
POTS
Dial-up Internet
 Mobile Telephony
 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
7
User Session Traffic Characterization
Web browsing session (TCP)
Packet Data Rate (bytes per second)
16000
14000
12000
10000
8000
6000
4000
2000
0
2800 2820 2840 2860 2880 2900 2920 2940 2960 2980 3000
Time duri ng Sess ion (s econds)
Packet Data Rate (bytes per second)
18000
Internet Telephony Audio – from Client
1750
1500
1250
1000
750
500
250
0
500 520 540 560 580 600 620 640 660 680 700
Time during Session (seconds)
7000
6000
5000
4000
3000
2000
1000
0
500 520 540 560 580 600 620 640 660 680 700
Time during Ses s ion (s ec onds )
2500
Packet Data Rate (bytes per second)
Packet Data Rate (bytes per second)
2000
Video Download (UDP)
Internet Telephony Audio – to Client
2500
2250
8000
2250
2000
1750
1500
1250
1000
750
500
250
0
500 520 540 560 580 600 620 640 660 680 700
Time during Session (seconds)
8
Typical Observations
•
•
200-second sections of sessions using three applications
Packet data traffic rates are provided in bytes per second
Browsing the World Wide Web 0
average = 2059
( TCP & HTTP )
• Bursty data traffic
16472
Peak-to-Average Bit Rate Ratio – 8.0
• Acquisition of various sources for a single site
Ratio of Download Byte Volume
• Long pauses by user
To Upstream – 8.8
• TCP upstream packet traffic volume moderate
Video + Audio Download
( UDP & VXtreme™ )
2853
average = 5232
7166
• UDP data uses fewer upstream packets than TCP
• Peak-to-Average data rate ratio low in this trace
Peak-to-Average Bit Rate Ratio – 1.37 • Mainly due to embedded constant bit rate
(CBR) audio stream of the downloaded sample
Ratio of Download Byte Volume
• Variable bit rates (VBR) are more common
To Upstream – 394.8
for most video applications
Interactive Internet Telephony 0
average = 1362
2474
( UDP & Internet Phone™ ) • Packet data rates reflect telephone speech patterns
Peak-to-Average Bit Rate Ratio – 1.85
Ratio of Download Byte Volume
To Upstream – 1.27
• Remote participant responsible for more speech
and packet traffic than client in this trace
• Byte volumes generally comparable
9
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
–
–
Intranet/
Internet
Server
Phase 1 – Vehicular mobility with a larger off-the-air receiver – May 2000
Phase 2 – Personal mobility with an integrated laptop receiver – Progressing
Proxy &
Router
Sprint PCS
10
4G System Research Areas
Adaptive
Antennas for
Broadband
Broadband
Air Interface
Research
Broadband
Implementations
4G System Design
11
Potential Coverage and Capacity Solutions
Primary Benefit
Improved Coverage
Higher Capacity
Asymmetric Data
Rate
High Power BTS
X
Lower Frequency
X
Small Cells
X
X
Adaptive Antennas
X
X
Advanced Air
Interface and Link
Adaptation
X
X
X
12
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
13
Closing
• 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
14