Fourth Generation Cellular Systems:

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21 Νοε 2013 (πριν από 3 χρόνια και 10 μήνες)

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1

Fourth Generation Cellular Systems:


Spectrum Requirements

Joseph M. Nowack

Member of the Technical Staff

Communication Systems and Technologies Labs

December 6, 2000


2




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
*

Is that your final
answer?

Service
provider
s

Cost
reductio
n

User
services

Wireless
wireline

Technolog
y trends

New
network

New air
interface

Wireless
Internet

4G will
not exist

Higher
bit rates

White
space

Strict
generatio
n

*
source: CSTL 4G white paper

Wireless
wireline

New
network

New air
interface

Technolog
y trends

Cost
reduction

Higher
bit rates

User
services

White
space

Service
provider
s

Wireless
Internet

3




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

Data Rate

Coverage

Area,

Mobility

Macrocell,

High Mobility

Microcell,

Limited Mobility

Fixed Access

64kbps

2Mbps

200Mbps

P
-
MP (LMDS)

Milli
-
wave LAN

2G

WLA
N

4G

3G

4




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

5









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
.
1
10
100
1000
1
10
100
1000
Data Rate or Carrier Frequency Increase Factor
Assumptions: Constant EIRP, constant Rx
antenna gain, no change in diffraction,
absorption or other propagation
characteristics. Path loss exponent = 4
Carrier Frequency
Data Rate
6




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



7




Broadband Wireless Content


Successful wireless services are preceded by growth of wired demand


POTS



䵯扩汥M呥汥灨潮y


䑩慬
-
異 䥮I敲湥琠




WA倬P䍥汬畬慲C䑡瑡


DSL, Cable Data




㑇⁂4潡摢慮搠坩牥汥ls



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

8









User Session Traffic Characterization

0
2000
4000
6000
8000
10000
12000
14000
16000
18000
2800
2820
2840
2860
2880
2900
2920
2940
2960
2980
3000
Packet Data Rate (bytes per second)
Time during Session (seconds)
Web browsing session (TCP)

Video Download (UDP)

Internet Telephony Audio


from Client

Internet Telephony Audio


to Client

0
250
500
750
1000
1250
1500
1750
2000
2250
2500
500
520
540
560
580
600
620
640
660
680
700
Packet Data Rate (bytes per second)
Time during Session (seconds)
0
250
500
750
1000
1250
1500
1750
2000
2250
2500
500
520
540
560
580
600
620
640
660
680
700
Packet Data Rate (bytes per second)
Time during Session (seconds)
0
1000
2000
3000
4000
5000
6000
7000
8000
500
520
540
560
580
600
620
640
660
680
700
Packet Data Rate (bytes per second)
Time during Session (seconds)
9









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

( TCP & HTTP )

Peak
-
to
-
Average Bit Rate Ratio


8.0

Ratio of Download Byte Volume

To Upstream


8.8

16472

0

average = 2059

• Bursty data traffic


• Acquisition of various sources for a single site


• Long pauses by user

• TCP upstream packet traffic volume moderate

Interactive Internet Telephony

( UDP & Internet Phone™ )

Peak
-
to
-
Average Bit Rate Ratio


1.85

Ratio of Download Byte Volume

To Upstream


1.27

2474

0

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

Video + Audio Download

( UDP & VXtreme™ )

Peak
-
to
-
Average Bit Rate Ratio


1.37

Ratio of Download Byte Volume

To Upstream


394.8

7166

2853

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

10




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

Sprint PCS

Intranet/

Internet
Server

Proxy &
Router

11




4G System Research Areas

Adaptive

Antennas for

Broadband

Broadband

Air Interface

Research

Broadband

Implementations

4G System Design

12




Potential Coverage and Capacity Solutions

Primary Benefit
Improved Coverage
Higher Capacity
Asymmetric Data
Rate
X
High Power BTS
X
Lower Frequency
X
Small Cells
X
X
Adaptive Antennas
X
X
Advanced Air
Interface and Link
Adaptation
X
X
13




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

14




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