802.11 standards - wireless networks
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A detailed presentation about 802.11 standards - wireless networksTRANSCRIPT
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Wireless Networks
By. P. Victer Paul
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Wireless Networks - Fundamentals
Two Types
Infrastructural Network Client/Server Hierarchy BSS – Basic Unit = One AP + One Station
Ad-Hoc Network Peer-to-Peer Scheme BSS / IBSS – Basic Unit = Two Stations
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Infrastructure Model includes:(most common)
• Stations (STA)– any wireless device
• Access Point (AP)– connects BSS to DS– controls access by STA’s
• Basic Service Set (BSS)– a region controlled by an AP– mobility is supported within a single
BSS
• Extended Service Set (ESS)– a set of BSS’s forming a virtual BSS– mobility is supported between BSS’s
in an ESS
• Distribution Service (DS)– connection between BSS’s
DS
BSS1
BSS2
BSS3STA1
STA2
STA3
ESS1
AP1
AP2
AP3
Wireless Networks - Fundamentals
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Ad Hoc Model includes:
• Stations (STA)– any wireless device– act as distributed AP
• Independent Basic Service Set (IBSS)– IBSS forming a self contained network– no AP and no connection to the DS
IBSS
STA1
STA2
STA3
Wireless Networks - Fundamentals
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Comparison between Ad Hoc and Infrastructure
• Infrastructure mode –
• More stability, scalability, ease of management and improved security
• Ad hoc does not provide security to that level and managing can be difficult incase of network growth. Performance suffers as we increase devices as well.
• Infrastructure mode
• High initial cost to for Access points (routers and switches)
Wireless Networks - Fundamentals
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Two types of access to air
DCF (Distributed Coordination Function )
means everybody can speak and try
to get air : 100% on the market
PCF (Point Coordination Function)
means ONE point coordinator (BOSS)
who will allowed you to speak
(like in bluetooth)
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MAC Classification
1. Type of Multiplexing: Depending on the dimension used for multiplexing we can classify the MAC layer a) Space Division Multiple access(SDMA) b) Time Division Multiple access(TDMA) c) Frequency Division Multiple access(FDMA) d) Code Division Multiple access(CDMA)
2. Based on Control: One can also classify the MAC layer on the basis of the way the control is achieved.
Centralized -- BSSDistributed -- IBSS
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MAC ClassificationCentralized Vs Distributed MAC control
Centralized (+) Easy to design (+) Easy management (+) Service Differentiation: Giving access according to the priority. ( - ) Central Bottleneck ( - ) Single point of failure
Distributed (+) Natural when there is no central information
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Goal of Wireless Standards
To develop a Medium Access Control (MAC) and Physical Layer (PHY) specification for wireless connectivity for fixed, portable and moving stations within a local area.
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Wireless Standards
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Wireless Standards
Wireless LANs
Standard is 802.11 Also Known as WiFi Higher Data Rate Longer Distance Coverage – So High Power Enhancements
802.11e – QoS 802.11i –Security 802.11n – Throughput 802.11h – Transmission Power control
Enhancement – No Explicit Policy, Only facilities will be provided
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Wireless Standards
Wireless PANs
Standard is 802.15…….. Lower Data Rate Shorter Distances – So Low Power Enhancements
802.15.1 – Bluetooth 802.15.3 – High Data Rate, but Short
Range 802.15.4 – Zigbee – WSN
Low cost, low power Multi functional & More number of devices
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Power Consumption in IEEE 802 Wireless Networks
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Power Management Techniques
Application Layer
Aimed at scheduling the applications or part of them
Application Layer Based Load Partitioning
Uses the power from base station Proxy based techniques
Adaptive based on the Power availability
Applications Based Database Techniques Video Processing
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Power Management Techniques
Transport Layer
Aimed to reduce the number of Retransmissions
The pa cket loss will not immediately interpreted
TCP-Probing
Wave-and-Wait Protocol
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Power Management Techniques
Network Layer
Aimed at efficient routing with minimal distance and hops
Backbone Based - Charge Based Clustering
Topology Control Based
Hybrid
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Power Management Techniques
Network Layer
Backbone Based - Charge Based Clustering Backbone Nodes - Always active Hops - Periodically sleep
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Power Management Techniques
Network Layer
Topology Control Based Reduce the power of overall transmission So, power of one hop transmission limited to
the range of the nearest neighbor.
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Power Management Techniques
Data Link Layer - LLC
Aimed at reducing the transmission overhead
Two Common Techniques
Automatic Repeat Request - ARQ The router itself enable the retransmission
rather than the receiver
Forward Error Correction – FEC codes Reduces the retransmission
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Power Management Techniques
Data Link Layer - LLC
Aimed at reducing the transmission overhead
Packet Scheduling Protocol Transmission of Multiple packets
Burst Mode of Transmission Only First packet needs preamble bytes All others follow piggyback
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Power Management Techniques
Data Link Layer - MAC
Two Common Techniques
Sleep Scheduling Protocols Aimed at reducing the power during ideal
listening of channels
Battery Aware MAC Protocols - BAMAC Priority will be given to the Low Charge Node to
transmit the packets
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Power Management Techniques
Data Link Layer - MAC
Sleep Scheduling Protocols
Aimed at reducing the power during ideal listening of channels
Synchronous Sleep Scheduler
Asynchronous Sleep Scheduler
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Power Management Techniques
Data Link Layer - MAC
Sleep Scheduling Protocols Synchronous Sleep Scheduler
Global Clock for all nodes in the set-up All nodes are active during “AWAKE” period and
inactive during “ASLEEP”
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Power Management Techniques Data Link Layer - MAC
Sleep Scheduling Protocols Asynchronous Sleep Scheduler
No Global Clock for all nodes in the set-up Transmitter may start to transmit at any time Receiver periodically checks the channel
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Power Management Techniques
Physical Layer
Two Common Practices Energy Saving
Remote Access Switch Enable the Receiver when only it has the Information
Energy Harvesting Increasing the Energy level from its surroundings
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Research Challenges in Power Management Wireless Networks
Hardware Level Energy Saving Energy Harvesting
Technique / Protocol Level
Programming Level
Debate between Hardware and Software
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Security in Wireless Networks
Authentication – Identification of Anticipated
There Cases User Does Something
User Has Something
User Knows Something
Authorization – Level of Access
Encryption
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Security WEP ( Wired Equivalent Privacy) 64/128 bits
Using RC4 algorithm, almost permanent key, very week security, able to crack by collecting statistic current security level for 99.9% products on the market.
TKIP (Temporal Key Integrity Protocol )
Used RC4 algorithm with a 128-bit "temporal key" but changes temporal keys every 10,000 packets and key depends on address and sequence number.
Will be required to obtain WiFi certification from 09/01/03
AES (Advanced Encryption Standard )
New, much more stronger encryption, protect against hacker frames in insertion. Need hardware accelerator. Optional feature.
Service Set Identifier (SSID) 802.1X Access Control
Wireless Protected Access (WPA) IEEE 802.11i
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Bandwidth in Wireless Networks
Very Peculiar because of a global medium
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Addressing in Wireless Networks
Traditional addressing – 3 types
Device addressing
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Roadmap of Wireless Standards
IEEE 802.11 - The original 1 Mbit/s and 2 Mbit/s, 2.4 GHz RF and IR standard IEEE 802.11a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001) IEEE 802.11b - Enhancements to 802.11 to support 5.5 and 11 Mbit/s (1999) IEEE 802.11d - International (country-to-country) roaming extensions IEEE 802.11e - Enhancements: QoS, including packet bursting IEEE 802.11F - Inter-Access Point Protocol (IAPP) IEEE 802.11g - 54 Mbit/s, 2.4 GHz standard (backwards compatible with b) (2003) IEEE 802.11h - 5 GHz spectrum IEEE 802.11i - Enhanced security IEEE 802.11j - Extensions for Japan IEEE 802.11k - Radio resource measurement enhancements IEEE 802.11n - Higher throughput improvements IEEE 802.11p - Wireless Access for the Vehicular Environment (ambulances and passenger
cars) IEEE 802.11r - Fast roaming IEEE 802.11s - Wireless mesh networking IEEE 802.11T - Wireless Performance Prediction (WPP) - test methods and metrics IEEE 802.11u - Interworking with non-802 networks (e.g., cellular) IEEE 802.11v - Wireless network management IEEE 802.11w - Protected Management Frames
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Roadmap of Wireless Standards
Gs Focus Technologies Standards1G Voice Analog Technology
FDMAAmerican Mobile Phone Systems (AMPS) - USNordic Mobile Telephone (NMT) – EuropeTotal Access Cellular System (TACS) - UKNTT - Japan
2G Voice Digital TechnologyTDMACDMA
US TDMA & US CDMAGlobal System for Mobile GSM) – EuropePacific Digital System (PDS) - Japan
3G Internet & Multimedia Services to the Mobile Users
Digital TechnologyTDMACDMA
Enhancements of the AboveInternational Mobile Telecommunications 2000(IMT – 2000)
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Roadmap of Wireless Standards
Divergence of US and European Standards
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Wireless Standards – Present Scenario
US and European Standards
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Some Comparisons
Advantages Disadvantages
•Mobility
•Ease of Installation
•Flexibility
•Cost
•Use unlicensed part of the radio spectrum
•Roaming
•Interference
•Degradation in performance
•High power consumption
•Low Speed
•Limited range
•Low Reliability
•Low Security
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Some Comparisons
Wi-Fi Wi-MAX802.11 802.16
limited in most cases to only 100 - 300 feet (30 - 100m).
Provide broadband wireless access (BWA) up to 30 miles (50 km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations.
Less Interference More Interference
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Some Comparisons
802.11 Wireless LAN Standards Comparison
802.11a 802.11b 802.11g Bluetooth
Data Rate (Mbps) 54 11 54721Kbps56Kbps
Operating Frequency (GHz)
5 2.4 2.4 2.4
Typical power output (mw)
40-800 100 100 100
CompatibilityNot compatible with 802.11b or 802.11g
Not compatible with 802.11a or 802.11g
Compatible with 802.11b
Not compatible with 802.11a/b.
Range 150feet 150feet 150feet 30feet
Interference risk Low High High High
Price Expensive Cheap Moderate Moderate
Hot-spot access Poor Good Good Poor