802.11 standards - wireless networks

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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


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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


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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)


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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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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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Network Layer

Aimed at efficient routing with minimal distance and hops

Backbone Based - Charge Based Clustering

Topology Control Based

Hybrid

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Network Layer

Backbone Based - Charge Based Clustering Backbone Nodes - Always active Hops - Periodically sleep

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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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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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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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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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Sleep Scheduling Protocols

Aimed at reducing the power during ideal listening of channels

Synchronous Sleep Scheduler

Asynchronous Sleep Scheduler

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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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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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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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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