Next Generation (NextG)

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Nov 21, 2013 (3 years and 4 months ago)

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Next Generation (NextG)

Wireless Networks

7/2/2004

Farid Farahmand

Outline


Description of wireless networks


Wireless network evolution


Wireless key technologies


Current researches

Wireless Networks


Motivated by
people
-
on
-
the
-
go


PCs availability, Internet usage, Mobile
life


Aimed is to establish wide
-
area voice
data communications


Includes mobile systems (cellular
telecommunication systems)


Wireless Network Evolution


First generation (1G): Analog voice systems


No standardization


Second Generation (2G): Digital voice systems


Currently deployed systems


CDMA, GSM (Global System for Mobile communication), PDC
(Japan) D
-
AMPS (Digital Advanced Mobile Phone System)


PCS Systems


Second Generation


advanced (2.5G): Combining voice and
data communications


Providing enhanced data rate


Two basic technologies:


GSM
-
based (high baud rate)


GPRS (General Packet Radio Service)


Utilizes voice time slots to send packet traffic


An overlay over the existing voice system


Should really be called 2.1G!!


Any standards?

Wireless Network Evolution


Third Generation (3G): Digital voice and
data communications


Developing a more general mobile network


Handling Internet access, email, messaging,
multimedia


Access to any services (voice, video, data, etc.)


Requires high quality transmission


Forth Generation (4G): All
-
IP mobile
networks


Ubiquitous wireless communications


Transparent to any services


Integrating multinetworks

Third Generation (3G)


Two basic proposals to handle voice and data


Ericsson: Universal Mobile Telecommunications systems (UMTS)


Compatible with European GSM


Backed by ETSI and Japan


Qualcom: CDM2000


Not compatible with GSM (cannot hand off called to GSM
-
based cells)


Compatible for IS
-
95 (supported by U.S)


3G Standards


1999 UMTS took over and an agreement was made over setting some
standards


A revolutionary technology with unlimited potential or not so great?


Major competing technologies


Bluethood


Wireless LAN (IEEE 802.x standards)


also known as WiFi


Short range wireless communications


Highly utilized and very popular: offices, airports, coffee shops, universities
and schools


Two basic modes of operations:


Ad
-
hoc networking: computers send data to one another


Access point:: sending data to the base station




Forth Generation
Wireless Networks


Otherwise known as NextG, Beyond 3G, 4G, and more!


Motivation


Providing all available services to highly mobile people (anytime anywhere)


Use your wireless device anywhere for listening to music, shopping (m
-
commerce) ,
downloading (file transfer), watching video (live streaming)


Multiple applications (talk and use Internet services at the same time)


Objectives


Total convergence of the wireless mobile and wireless access communications
(developing a broadband wireless network)


Ubiquitous wireless communications and services


Integration of multi
-
networks using IP technology


Similar technology to the wired Internet where users are freed from their local
networks


All
-
IP based wireless networks


Not just IP end
-
to
-
end but
over
-
the
-
air

packet switching


Supporting native wireless IP mode


Highly integrated


High bandwidth / high
-
speed wireless


Highly compatible with wired network infrastructures


ATM, IP, ATM

4G Technology Challenges


Supporting heterogeneous multitude of systems


Includes multiple networks:


Cellular telecommunication systems


Digital video broadband


Digital audio broadband


Wireless LAB, Bluethood
-
based networks


Open communication network: infrastructure independent which can access to any
services and applications (now and in the future!)


Complete compatibility between wireless and wired networks through gateways


Supporting statistical multiplexing of heterogeneous data over
-
the
-
air


Latency, noisy environment, unpredictable discontinuities and loss, etc.


High
-
speed wireless transmission over the air


High performance physical layer


20Mbps (2G: 28Kbps, 3G: 2Mbps)


Scarce bandwidth availability


Efficient frequency spectrum utilization


Efficient hand off


Dynamic bandwidth allocation


Advanced digital transmission technology (modulation, low power devices, etc.)

4G Key Issues
-

Research Areas


IP Addressing


Mobile IPv6 protocol provides unbroken connectivity between mobile nodes


Architecture


Horizontal communications between different access technologies using gateways


Including local
-
area access technology (3G only covers wide
-
area packet switched
cellular technology)


Hand off


Fast hand off due to high
-
speed transmission


High reliability


QoS framework


Interoperability between wireless and wired networks


QoS classes: Conversational (most delay sensitive), streaming, interactive,
background (least delay sensitive)


Fair bandwidth allocation


Class
-
based QoS over the air






4G Key Issues
-

Research Areas


Security and billing


Essential in e
-
commerce


More than just authentication and encryption (as in 3G)


End
-
to
-
end security mechanisms between the Internet server (wired) and the
mobile terminal


No translation and decomposition of the data at the gateways


Usage fee


Volume based or time
-
based?


TCP performance in wireless / mobile communications


Research shows unmodified standard TCP is not well aligned with cellular
boundaries


New protocols have been developed: Snoop, Split connections, other end
-
to
-
end protocol families


Using Snoop agent the exchange of TCP packets and ACKs are monitored and
performs local retransmissions as needed (OBS
-
like!)


Split
-
connections deals with wireless and wired network inconsistencies (gateways,
translations, etc.)


Two separate connections between fixed and mobile hosts


End
-
to
-
end protocols deal with retransmission timeout causing the TCP window to
shrink too often



QoS
-
enabled MAC Protocol
-

Scheduling Problem



Mac protocols:


Wirelines: FIFO, Generalized Processor Sharing (GPS)


Wireless: Random Access Protocols


Voice
-
based MAC protocols don’t work well for multimedia applications


No packet ordering is supported, no fair packet loss sharing


Multimedia traffic exhibit highly bursty traffic rates


Each class of traffic has a QoS requirement and traffic rate characteristics


A new MAC protocol with fair packet loss sharing scheduling for 4G is proposed


Assumes time
-
division/code
-
division multiple access wireless system with IP transmission


Objective (conflicting):


support as many users as possible (high channel utilization),


dropped packets between all users are shared fairly


Basic Idea:


Allocate minimum amount of resources to satisfy the QoS requirements


Maximize the total number of scheduled packets


How to calculate the number of packets dropped:


Give enough BW to meet the QoS guaranteed level, drop the rest


Maximize the number of packets sent: bin
-
packing problem


Blocks

Bins

Pack

IP Pkts

Time Slots

Class
-
based QoS over Air
Interface in 4G


Basic characteristics:


Flexible (support various services)


Effective (easy negotiation mechanism to handle QoS over air)


Basic Idea:


Check congestion over the air


When congestion occurs, users with lower QoS have to back off
their transmission rate


The extent of the back off depends on the class it belongs to


Basic problem is possible under
-
utilization


Supports any number of QoS classes based on the specified
resource assignment for each class


Wireless

Internet

Bkbone

QoS Over Air