Transcript Next Generation (NextG) Wireless Networks

Next Generation (NextG)
Wireless Networks
7/2/2004
Farid Farahmand
Outline
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Description of wireless networks
Wireless network evolution
Wireless key technologies
Current researches
Wireless Networks
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Motivated by people-on-the-go
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PCs availability, Internet usage, Mobile
life
Aimed is to establish wide-area voice
data communications
Includes mobile systems (cellular
telecommunication systems)
Wireless Network Evolution
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First generation (1G): Analog voice systems
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Second Generation (2G): Digital voice systems
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No standardization
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
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Providing enhanced data rate
Two basic technologies:
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GSM-based (high baud rate)
GPRS (General Packet Radio Service)
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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
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Third Generation (3G): Digital voice and
data communications
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Developing a more general mobile network
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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
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Ubiquitous wireless communications
Transparent to any services
Integrating multinetworks
Third Generation (3G)
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Two basic proposals to handle voice and data
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Ericsson: Universal Mobile Telecommunications systems (UMTS)
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Qualcom: CDM2000
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Not compatible with GSM (cannot hand off called to GSM-based cells)
Compatible for IS-95 (supported by U.S)
3G Standards
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Compatible with European GSM
Backed by ETSI and Japan
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
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Bluethood
Wireless LAN (IEEE 802.x standards) – also known as WiFi
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Short range wireless communications
Highly utilized and very popular: offices, airports, coffee shops, universities
and schools
Two basic modes of operations:
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Ad-hoc networking: computers send data to one another
Access point:: sending data to the base station
Forth Generation Wireless Networks
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Otherwise known as NextG, Beyond 3G, 4G, and more!
Motivation
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Providing all available services to highly mobile people (anytime anywhere)
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Use your wireless device anywhere for listening to music, shopping (m-commerce) ,
downloading (file transfer), watching video (live streaming)
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Multiple applications (talk and use Internet services at the same time)
Objectives
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Total convergence of the wireless mobile and wireless access communications
(developing a broadband wireless network)
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Ubiquitous wireless communications and services
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Integration of multi-networks using IP technology
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Similar technology to the wired Internet where users are freed from their local
networks
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All-IP based wireless networks
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Not just IP end-to-end but over-the-air packet switching
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Supporting native wireless IP mode
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Highly integrated
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High bandwidth / high-speed wireless
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Highly compatible with wired network infrastructures
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ATM, IP, ATM
4G Technology Challenges
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Supporting heterogeneous multitude of systems
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Includes multiple networks:
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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
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Cellular telecommunication systems
Digital video broadband
Digital audio broadband
Wireless LAB, Bluethood-based networks
Latency, noisy environment, unpredictable discontinuities and loss, etc.
High-speed wireless transmission over the air
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High performance physical layer
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20Mbps (2G: 28Kbps, 3G: 2Mbps)
Scarce bandwidth availability
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Efficient frequency spectrum utilization
Efficient hand off
Dynamic bandwidth allocation
Advanced digital transmission technology (modulation, low power devices, etc.)
4G Key Issues - Research Areas
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IP Addressing
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Architecture
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Horizontal communications between different access technologies using gateways
Including local-area access technology (3G only covers wide-area packet switched
cellular technology)
Hand off
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Mobile IPv6 protocol provides unbroken connectivity between mobile nodes
Fast hand off due to high-speed transmission
High reliability
QoS framework
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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
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Security and billing
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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
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Usage fee
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No translation and decomposition of the data at the gateways
Volume based or time-based?
TCP performance in wireless / mobile communications
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Research shows unmodified standard TCP is not well aligned with cellular
boundaries
New protocols have been developed: Snoop, Split connections, other end-toend protocol families
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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.)
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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 ProtocolScheduling Problem
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Mac protocols:
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Voice-based MAC protocols don’t work well for multimedia applications
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Wirelines: FIFO, Generalized Processor Sharing (GPS)
Wireless: Random Access Protocols
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
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Assumes time-division/code-division multiple access wireless system with IP transmission
Objective (conflicting):
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Basic Idea:
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support as many users as possible (high channel utilization),
dropped packets between all users are shared fairly
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:
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Give enough BW to meet the QoS guaranteed level, drop the rest
Maximize the number of packets sent: bin-packing problem
Pack
Blocks
IP Pkts
Bins
Time Slots
Class-based QoS over Air
Interface in 4G
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Basic characteristics:
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Basic Idea:
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Flexible (support various services)
Effective (easy negotiation mechanism to handle QoS over air)
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
QoS Over Air
Wireless
Internet
Bkbone