ICOM 6505: Wireless Networks Introduction

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ICOM 6505 Wireless Networks- Introduction -

• By Dr. Kejie Lu
• Department of Electronic and Computer Engineering
• Spring 2009

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Course Outlines

• Introduction and Overview
• Wireless Network Designs
• Characteristics of the Wireless Medium
• Medium Access Control for Wireless Links
• Mobility Support in Internet and Mobile IP
• Route Optimization in Mobile IP
• Wireless TCP
• Wireless Networking Security Issues
• Example Wireless Networks
• Cellular Networks
• Wireless Local Area Networks
• Mobile Ad Hoc Networks
• Wireless Sensor Networks
• Project Presentations

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Why This Course is Important?

• Wireless networking is one of the most important
  technologies today!
• One of the biggest markets!
• Job opportunities

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Wireless Communication Systems

• Wireless Communication System
• Any electrical communication system that uses a
  naturally occurring communication channel, such
  as air, water, earth
• Examples
• Broadcast Radio, TV, pagers, satellite TV, etc.
• Two Way walkie talkie, cell phones, satellite
  phones, Wireless Local Area Networks, etc.
• Fundamentally different from wired networks

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Wireless vs. Mobile

• Wireless ? mobile !
• Wireless node may be static and fixed
• E.g., WiMAX or IEEE 802.16 Broadband wireless
  access (BWA)
• Mobile node may be using a wireline networking
• E.g., laptop with Ethernet link
• Different techniques will be used to tackle
  either of them!

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Wireless Issues

• Wireless link implications
• Communications channel is the air
• poor quality fading, shadowing, weather, etc.
• Regulated by governments
• frequency allocated, licensing, etc.
• Limited bandwidth
• Low bit rate, frequency planning and reuse,
  interference
• Power issues
• Power levels regulated (safety issues), conserve
  mobile terminal battery life
• Security issues
• wireless channel is a broadcast medium!

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Mobility Issues

• Mobility Types
• User mobility user can access network while
  mobile
• must handoff calls/connections in progress as
  user moves
• track users as they move so they can receive
  info/calls
• Service mobility users services follow them
• Need to have authentication and services follow
  user
• Mobile devices gt portable device
• Carry own power supply (limited power)
• Limited memory and CPU power
• Limited user interface
• Degree of Mobility
• Geographic range speed (e.g., cordless vs. car
  phone)

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Main Points

• The wireless vision encompasses many exciting
  systems and applications
• Technical challenges transcend across all layers
  of the system design
• Wireless systems today have limited performance
  and interoperability
• Standards and spectral allocation heavily impact
  the evolution of wireless technology

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How many Wireless Tech.?
Wireless e-mail You can use wireless API to
build meaningful GUI App
Application Layer
Wireless TCP, CAC (end-to-end virtual connection,
)
Transport Layer
Mobile IP, mobility/location management, GPS
(routing problem)
Network Layer
MAC (CDMA, CSMA/CA in WLAN), Error Control (FEC),
(wireless access)
Data Link Layer
Propagation (fading, multipath, path-loss model),
modulation, encoding, antenna
Physical Layer
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Future Wireless Systems
Ubiquitous Communication Among People and Devices
Nth Generation Cellular Wireless LANs Wireless Ad
Hoc Networks Wireless Sensor Networks Remote
Learning/Medicine Automated Vehicles/Robots All
these and more
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Technical Challenges

• Hardware
• Small, lightweight, multimode, low power
• High-frequency components
• Communication Link Design
• Channel models
• Fast, robust, spectrally efficient communication
  techniques
• Mitigation of wireless channel impairments
• Multiple Access and Resource Allocation
• Efficient schemes that maximize system capacity
• Dynamic resource allocation and efficient
  spectral reuse
• Networking
• Routing and mobility management for mobile users
• Network reliability, flexibility, and scalability
• Deliver QoS to applications/application
  adaptation
• Performance gap with wire-line systems.

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Multimedia Requirements
Voice
Video
Data
Delay
lt100ms
-
lt100ms
Packet Loss
lt1
0
lt1
BER
10-3
10-6
10-6
Data Rate
8-32 Kbps
1-100 Mbps
1-20 Mbps
Traffic
Continuous
Bursty
Continuous
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Current Wireless Systems

• Fixed Wireless Access
• Cellular Systems
• Wireless LANs
• Satellite Systems
• Paging Systems
• Wireless Ad Hoc network
• Bluetooth
• Sensor Networks
• etc.

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Cellular Network Architecture

• Cellular Systems
• provide wireless coverage to a geographic area
  with a set of slightly overlapping cells
• Cellular/PCS Network Components
• Mobile Station (Terminal) handset
• Base Station (cell site) - provides radio
  channels between mobile units and network.
• Base Station Controller (BSC) - manages a cluster
  of BS, channel assignment, handoff, power
  control, some switching, etc.
• Mobile Switching Center (MSC)- provides switching
  functions, coordinates location tracking, call
  delivery, handoff, interfaces to HLR,VLR, AUC,
  etc..
• HLR/VLR/AUC (Home Location Register/Visitor
  Location Register/Authentication Center)
  databases to track, bill and authenticate users

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System Capacity

• System Capacity is the number all users that can
  communicate (use the system) at the same time.
• A base station (cell) has a fixed number of
  channels available, hence at a given time a fixed
  number of users can talk simultaneously

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Cellular SystemsReuse channels to maximize
capacity

• Geographic region divided into cells
• Frequencies/timeslots/codes reused at
  spatially-separated locations.
• Co-channel interference between same color cells.
• BS/MSC coordinate handoff and control functions
• Shrinking cell size increases capacity, as well
  as networking burden

MSC
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System Capacity(C) and Coverage Area(d2)
System 1
System 1
System 2
System 2
d1
d2
Low cost base-stations covering a small area
High cost base-stations covering a large area
Each base station has a fixed number of channels
for both systems All channels in System1 9 x
All channels in System2
C1 / C2 (d2 / d1)2
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3G Cellular Design Voice and Data

• Data is bursty, whereas voice is continuous
• Different access and routing strategies
• Need to widen the data pipe
• 384 Kbps outdoors, 1 Mbps indoors.
• Standard based on wideband CDMA (IMT-2000) and
  CDMA2000.
• Adaptive techniques and more bandwidth yield high
  rates
• Evolution of existing systems (2G and 2.5G)
• GSMEDGE
• IS-95(CDMA)
• What is beyond 3G?

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4G Cellular Design

• Reasons to Have 4G
• Support interactive multimedia services
  teleconferencing, wireless Internet, etc.
• Wider bandwidths, higher bit rates.
• Global mobility and service portability.
• Low cost.
• Scalability of mobile networks.
• What's New in 4G
• Entirely packet-switched networks.
• All network elements are digital.
• Higher bandwidths to provide multimedia services
  at lower cost (up to 100Mbps).
• Tight network security.

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Satellite Based Mobile Systems

• Categorized as
• Two-way (or one-way) limited quality voice or
  data transmission
• Very wide range and coverage
• Large regions
• Sometimes global coverage
• Very useful in sparsely populated areas rural
  areas, sea, mountains, etc.
• Target Vehicles and/or other stationary/mobile
  uses
• Expensive base station (satellites) systems
• Different orbit heights
• GEOs (39000 Km) versus LEOs (2000 Km)

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Paging Systems

• Broad coverage for short messaging
• Message broadcast from all base stations
• Simple terminals
• Optimized for 1-way transmission
• Answer-back hard
• Cellular taking over

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Wireless Local Area Networks (WLANs)

• Wireless Local Area Networks
• Support communication to mobile data users via
  wireless channel around a typical range of 100m.
• IEEE 802.11a, 11b standard (wireless Ethernet)
• 1Mbps, 2Mbps, 11Mbps, (a standard) 54 Mbps rates
• Infrastructure based and Ad-Hoc based networks
• Wireless LAN market
• Medical
• Education
• Manufacturing
• Retail
• Public Access (Hotels, airports, coffee shops,
  etc.)

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WLAN Standards
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Wireless Ad-Hoc Networks

• Mobile Ad-Hoc Network (MANET)
• No fixed infrastructure
• Nodes connect via wireless links
• Network devices are part of the network
• act as routers for traffic without a direct
  wireless link (Mulit-hop connections)
• Nodes are mobile and can move in arbitrary
  fashion
• Topology and connections change frequently
• Mobile Ad-Hoc networks are network architecture
• that can be rapidly deployed
• that do not rely on pre-existing infrastructure
• whose set of nodes is continuously changing
• which self-adapts to the connectivity and
  propagation patterns, and
• which adapts to the traffic and mobility patterns

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Characteristics of Ad-Hoc Networks

• The distinctive differences between ad-hoc
  networks and cellular networks are
• No fixed infrastructure is present
• Multi-hop routing (network diameter gtgt node
  transmission range)
• Peer-to-peer operation
• Frequent changes of associations

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Use of the Ad-Hoc Technology for Military
Communications
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Challenges in Ad-Hoc Networks

• The challenges in the design of Ad-Hoc networks
  stem from the following facts
• The lack of centralized entity ? self-organizing
  and distributed protocols
• The possibility of rapid platforms movement
  (highly versatile topology) ? efficient and
  robust protocols
• All communication is carried over the wireless
  medium ? power and spectrum efficient
  communications
• Compare this with the fixed (cellular) networks

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The Merits of Infrastructure

• Wireless mesh network

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Bluetooth

• Cable replacement RF technology (low cost)
• Short range (10m, extendable to 100m)
• 2.4 GHz band (crowded)
• 1 Data (700 Kbps) and 3 voice channels
• Widely supported by telecommunications, PC, and
  consumer electronics companies
• Interesting applications starting to emerge

8C32810.61-Cimini-7/98
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3G Hybrid Network

• Cellular networks
• wide area coverage
• Wireless LAN
• higher speed
• lower operating and equipment cost
• GPRS and 3G provide global coverage, mobility and
  Quality of Service.
• WLAN is designed to cover small areas such as
  small hot spot locations.