SNJB’s KBJ COE, Chandwad

By B.A.Khivsara

Assistant Professor

SNJB’s KBJ COE, Chandwad

Wireless LAN Basics

Wireless Standards (802.11 a/b/g/n/ac/ad)

Wireless LAN and Technology,

Wireless application protocols Architecture

Wireless application protocols application

Wireless LAN Basics





LANs provide connectivity for interconnecting computing resources at the local levels of an organization

Wired LANs

Limitations because of physical, hard-wired infrastructure

Wireless LANs provide

Flexibility

Portability

Mobility

Ease of Installation

Types◦ Infrastructure based

◦ Ad-hoc

Advantages◦ Flexible deployment

◦ Minimal wiring difficulties

◦ More robust against disasters (earthquake etc)

◦ Historic buildings, conferences, trade shows,…

Disadvantages◦ Low bandwidth compared to wired networks (1-10 Mbit/s)

◦ Proprietary solutions

◦ Need to follow wireless spectrum regulations

Infrastructure Network

ad-hoc network

APAP

AP

wired network

AP: Access Point

Source: Schiller

Medical Professionals

Education

Temporary Situations

Airlines

Security Staff

Emergency Centers

Access point (AP): A station that provides access

to the DS.

Basic service set (BSS): A set of stations controlled

by a single AP.

Distribution system (DS): A system used to

interconnect a set of BSSs to create an ESS.

Extended service set (ESS):Two or more BSS

interconnected by DS

Hidden terminals◦ A and C cannot hear each other.◦ A sends to B, C cannot receive A. ◦ C wants to send to B, C senses a “free” medium (CS fails)◦ Collision occurs at B.◦ A cannot receive the collision (CD fails).◦ A is “hidden” for C.

Solution? (MAC layer)◦ Hidden terminal is peculiar to wireless (not found in wired)◦ Need to sense carrier at receiver, not sender!◦ “virtual carrier sensing”: Sender “asks” receiver whether it can

hear something. If so, behave as if channel busy.

BA C

MAC layer covers three functional areas:Reliable data delivery

Access control

Security

Loss of frames due to noise, interference, and propagation effects

Frame exchange protocolSource station transmits dataDestination responds with acknowledgment (ACK)If source doesn’t receive ACK, it retransmits frame

Four frame exchange for enhanced reliabilitySource issues request to send (RTS)Destination responds with clear to send (CTS)Source transmits dataDestination responds with ACK

Asynchronous data service (DCF)CSMA/CARTS/CTS

Time bounded service (PCF)

Polling

Inter-frame spacing (IFS)

DIFS

PIFS

SIFS

CSMA/CD – CSMA/Collision detectionFor wire communication

No control BEFORE transmission

Generates collisions

Collision Detection-How?

CSMA/CA – CSMA/Collision AvoidanceFor wireless communication

Collision avoidance BEFORE transmission

Why avoidance on wireless?

Difference in energy/power for transmit & receive

Difficult to distinguish between incoming weak signals, noise, and effects of own transmission

802.11 avoids the problem of hidden terminals

◦ A and C want to send to B

◦ A sends RTS to B

◦ B sends CTS to A

◦ C “overhears” CTS from B

◦ C waits for duration of A’s transmission

A B C

RTS

CTSCTS

DIFS: Distributed IFS(Inter Frame Space) RTS: Request To SendSIFS: Short IFSCTS: Clear To SendACK: AcknowledgementNAV: Network Allocation VectorDCF: Distributed Coordination Function

Defined length of time for control

SIFS - Short Inter Frame Spacing

Used for immediate response actions

e.g ACK, CTS

PIFS - Point Inter Frame Spacing

Used by centralized controller in PCF scheme

DIFS - Distributed Inter Frame Spacing

Used for all ordinary asynchronous traffic

DIFS (MAX) > PIFS > SIFS (MIN)

Wireless LAN Basics





In response to lacking standards, IEEE developed the first

internationally recognized wireless LAN standard – IEEE 802.11

IEEE published 802.11 in 1997, after seven years of work

Most prominent specification for WLANs

Scope of IEEE 802.11 is limited to Physical and Data Link Layers.

Appliance Interoperability

Fast Product Development

Stable Future Migration

Price Reductions

The 802.11 standard takes into account the following significant differences between wireless and wired LANs:

Power Management

Security

Bandwidth

IEEE 802.3

CarrierSense

IEEE 802.4

TokenBus

IEEE 802.5

TokenRing

IEEE 802.11

Wireless

IEEE 802.2Logical Link Control (LLC)

PHYOSI Layer 1(Physical)

Mac

OSI Layer 2(Data Link)

802.11-1997 (802.11 legacy) 802.11a (OFDM Waveform) 802.11b 802.11g 802.11-2007 802.11n 802.11-2012 802.11ac 802.11ad 802.11af 802.11ah 802.11ai 802.11aj 802.11aq 802.11ax

•Operating in 2.4 GHz ISM band

•Lower cost, power consumption

•Most tolerant to signal interference

Frequency-

hopping spread

spectrum

•Operating in 2.4 GHz ISM band

•Supports higher data rates

•More range than FH or IR physical layers

Direct-sequence

spread

spectrum

•Lowest cost

•Lowest range compared to spread spectrum

•Doesn’t penetrate walls, so no eavesdropping

Infrared

Spread spectrum is a form of wireless communications in

which the frequency of the transmitted signal is

deliberately varied. This results in a much greater

bandwidth than the signal would have if its frequency

were not varied

This technique decreases the potential interference to

other receivers while achieving privacy.

Two types- FHSS and DSSS

Signal is broadcast over seemingly random series of radio frequenciesSignal hops from frequency to frequency at

fixed intervalsReceiver, hopping between frequencies in

synchronization with transmitter, picks up messageAdvantages

Efficient utilization of available bandwidthEavesdropper hear only unintelligible blipsAttempts to jam signal on one frequency succeed only at knocking out a few bits

Each bit in original signal is represented by multiple bits in the transmitted signalSpreading code spreads signal across a wider

frequency band DSSS is the only physical layer specified for

the 802.11b specification802.11a and 802.11b differ in use of chipping method 802.11a uses 11-bit barker chip

802.11b uses 8-bit complimentary code keying (CCK) algorithm

FH systems use a radio carrier that “hops” from frequency to frequency in a pattern known to both transmitter and receiver◦ Easy to implement

◦ Resistance to noise

◦ Limited throughput (2-3 Mbps @ 2.4 GHz)

DS systems use a carrier that remains fixed to a specific frequency band. The data signal is spread onto a much larger range of frequencies (at a much lower power level) using a specific encoding scheme.◦ Much higher throughput than FH (11 Mbps)

◦ Better range

◦ Less resistant to noise (made up for by redundancy – it transmits at least 10 fully redundant copies of the original signal at the same time)

IEEE 802.11 standards :

IEEE 802.11 standards

IEEE 802.11 b

IEEE 802.11 a

IEEE 802.11 g

IEEE 802.11 n

IEEE 802.11 ac

IEEE 802.11 ad

30


IEEE 802.11 b

31

Frequency = 2.4 GHz (ISM band)

Maximum Speed =11 Mbps

Range = about 38meters(Varies)

Encoding Scheme = DSSS

Modulation Technique= BPSK(1 Mbps),

DQPSK(2 Mbps), CCK(5.5 Mbps,11Mbps)

www.cisco.com


IEEE 802.11 b

32

Pros of 802.11b - lowest cost; signal range is good and not easily obstructedCons of 802.11b - slowest maximum speed; home appliances may interfere on the unregulated frequency band

www.cisco.com



IEEE 802.11 b

IEEE 802.11 a

IEEE 802.11 g

IEEE 802.11 n

IEEE 802.11 ac

IEEE 802.11 ad

33


IEEE 802.11 a

34

Frequency = 5 GHz

Maximum Speed = 54 Mbps

Range = about 35 meters(Varies)

Encoding Scheme = OFDM

www.cisco.com


35

IEEE 802.11 a

Multipath Effect(Multipath Fading)

is simply a term used to describe the multiple

Paths the radio wave may follow between

transmitter and receiver


36

IEEE 802.11 a

Orthogonal Frequency Division Multiplexing(OFDM)

OFDM a digital multi-carrier modulation method. A large

number of closely-spaced orthogonal sub-carriers are used to

carry data.

OFDM is popular for wideband communications today by way

of low-cost digital signal processing components

Ultra-high spectrum efficiency◦ 5 GHz band is 300 MHz (vs. 83.5 MHz @ 2.4 GHz)

◦ More data can travel over a smaller amount of bandwidth

High speed◦ Up to 54 Mbps

Less interference◦ Fewer products using the frequency 2.4 GHz band shared by cordless phones, microwave

ovens, Bluetooth, and WLANs

Standards and Interoperability

◦ Standard not accepted worldwide

◦ Not compatible or interoperable with 802.11b

Legal issues

◦ License-free spectrum in 5 GHz band not available worldwide

Market

◦ There is limited interest for 5 GHz adoption

Cost◦ 2.4 GHz will still has >40% cost advantage

Power consumption◦ Higher data rates and increased signal require more power

OFDM is less power-efficient than DSSS

Building-to-building connections

Video, audio conferencing/streaming video,

and audio

Large file transfers, such as engineering

CAD drawings

Faster Web access and browsing



IEEE 802.11 b

IEEE 802.11 a

IEEE 802.11 g

IEEE 802.11 n

IEEE 802.11 ac

IEEE 802.11 ad

40


IEEE 802.11 g

41

Frequency= 2.4 GHz

Maximum Speed = 54 Mbps



Backward compatibility with 802.11 b devices

www.cisco.com


IEEE 802.11 g

42

•Pros of 802.11g -

fast maximum speed;

signal range is good and not easily obstructed

•Cons of 802.11g -

costs more than 802.11b;

appliances may interfere on the unregulated

signal frequency

Provides higher speeds and higher capacity requirements for applications

Leverages Worldwide spectrum availability in 2.4 GHz

Less costly than 5 GHz alternatives

Provides easy migration for current users of 802.11b WLANs◦ Delivers backward support for existing 802.11b

products

Provides path to even higher speeds in the future



IEEE 802.11 b

IEEE 802.11 a

IEEE 802.11 g

IEEE 802.11 n

IEEE 802.11 ac

IEEE 802.11 ad

44


IEEE 802.11n

45

Frequency = 5 GHz,2.4 GHz

Modulation = OFDM

Addition of MIMO (Multiple Input Multiple Output)

Speed = 54 Mbit/s to 600 Mbit/s




IEEE 802.11 n

Multiple Input Multiple Output(MIMO)

46

In radio, Multiple-input and

Multiple-output is used of

multiple antennas at both the

transmitter and receiver to

improve communication

performance.


47

Pros of 802.11n -•fastest maximum speed and best signal range;• more resistant to signal interference from outside sources

Cons of 802.11n -•standard is not yet finalized; •costs more than 802.11g; •the use of multiple signals may greatly interfere with nearby 802.11b/g based networks.



IEEE 802.11 b

IEEE 802.11 a

IEEE 802.11 g

IEEE 802.11 n

IEEE 802.11 ac

IEEE 802.11 ad

48


IEEE 802.11ac

49

Frequency = 5 GHz

Modulation = OFDM

Addition of MIMO (Multi User-Multiple Input Multiple Output)

Speed = 433.3 Mbit/s per spatial stream, 1.3 Gbit/s

total


IEEE 802.11ac - Features

50

Extended channel bindingMore MIMO spatial streamsMultiple STAs, each with one or more antennas, transmit or receive independent data streams simultaneouslyModulation- 256-QAMBeamforming with standardized sounding and feedback for compatibility between vendors

http://en.wikipedia.org/wiki/MIMO

http://en.wikipedia.org/wiki/Station_(computer_networking)

http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation

http://en.wikipedia.org/wiki/Beamforming


IEEE 802.11ac- MIMO

51


IEEE 802.11ac Applications

52

Highly interactive video gaming, video conferencing, High definition video streaming andMany more applications that need data at rates that push the boundaries of exiting Wi-Fi systems.



IEEE 802.11 b

IEEE 802.11 a

IEEE 802.11 g

IEEE 802.11 n

IEEE 802.11 ac

IEEE 802.11 ad

53


IEEE 802.11ad

54

Frequency = 60GHz

Speed = 7Gbps

Antenna Technology = Uses Beamforming

Modulation = OFDM

Wireless LAN Basics





WAP Introduction

Architecture overview

Components of WAP architecture

Applications, Advantages & Disadvantages of WAP

o WAP stands for Wireless Application Protocol o WAP is an application communication protocol o WAP is used to access services and information o WAP is inherited from Internet standards o WAP is for handheld devices such as mobile

phones o WAP is a protocol designed for micro browsers o WAP enables the creating of web applications

for mobile devices. o WAP uses the mark-up language WML (not

HTML) WML is defined as an XML 1.0 application

The basic AIM of WAP is to provide a web-like experience on small portable devices- like mobile phones and PDAs

Purpose of WAP

To enable easy, fast delivery of relevant information andservices to mobile users.

Type of devices that use WAP

Handheld digital wireless devices such as mobile phones,pagers, two-way radios, smart phones and communicators-- from low-end to high-end.

Type of OS that use WAP

It can be built on any operating system including Palm OS,EPOC 32, Windows CE, FLEXOS, OS/9, Java O

WAP works with most Wireless networks such as:

CDPD, CDMA, GSM, PDC, PHS, TDMA, FLEX, ReFLEX, iDEN, TETRA, DECT, DataTAC, Mobitex.

WAP Introduction




WWW programming model is optimized and

extended to match characteristics of the wireless

environment

Utilizes proxy technology to connect between the

wireless domain and WWW

CGI, Scripts,Etc.

Content

Web Server

Client

WebBrowser

Request(URL)

Response(Content)

CGI, Scripts,Etc.

Content

Web Server

Client

WAEUserAgent

Request(URL)

Response(Content)

Gateway

EncodersAnd Decoders

EncodedRequest

EncodedResponse

WAP Device

- Is used to access WAP applications and content. It might be a PDA,

handheld computer.

WAP Client

- Entity that receives content from Internet via a WAP Gateway. This is

usually the WAP Browser.

WAP Content/Origin/Application Server

- Element in the network where the information or web/WAP

applications resides.

WAP Proxy

- Acts both as a client and as a server in the network . Typically has

◦ Protocol gateway : translates requests from the WAP protocol stack

to WWW protocol stack

◦ Content encoders and decoders : translate WAP content into compact

encoded formats to reduce the size of data over the network

WAP Gateway

- Intermediary element used to connect two different types of network. It receives request directly from the clients as if it actually were the origin server that clients want to receive the information form. The clients are usually unaware that they are speaking to the Gateway.

WAP Browser

◦ Software running on the WAP device that interprets the WAP content arriving from the internet and decides how to display it on WAP device.

WML

o WML – Wireless Markup Language

o Is a tag language that allows the text portions of Web Pages to be presented on cellular phones and Personal Digital Assistants (PDAs) via wireless access.

o WML is used for delivering data to WAP devices, and is HTML- like in its appearance.

TCP/IPUDP/IP

TLS - SSL

HTTP

HTMLJava Script

WAP Introduction




Other ServicesAnd Applications

Transport Layer (WDP)

Security Layer (WTLS)

Transaction Layer (WTP)

Session Layer (WSP)

Application Layer (WAE)

GSM CDMA PHS IS-136 CDPD PDC-P FLEX Etc…

Bearers :

General-purpose application environment based on

a combination of WWW and mobile telephony

technologies.

It defines the user interface on the phone. It

contains WML and WTA (Wireless Telephony

Application).

Primary objective – interoperable environment.

WAE includes a micro-browser .Various

components of WAE are:

◦ Addressing model –uses URL & URI

◦ WML- similar feature like HTML

◦ WML script –For user I/P validation

◦ WTA(Wireless Telephony Application)

◦ Content formats

The WAP session protocol (WSP) layer provides a lightweight session layer to allow efficient exchange of data between applications.

Application layer with a consistent interface for two session services◦ Connection-oriented service that operates

above the transaction layer protocol (WTP)◦ Connectionless service that operates above a

secure or non-secure datagram service (WDP)

Optimized for low-bandwidth bearer networks with long latency

Establish and releasing a reliable session between client and server

Exchange content between client & server using compact encoding

Suspend & resume session

Provide HTTP 1.1 functionality

Exchange client & server session headers

Interrupt transactions in process

Push content from server to client in an unsynchronized manner

Light weight transaction-oriented protocol suitable for “ thin client”

Provides reliability to the datagram service through the use of unique transaction identifier , acknowledgements, retransmission duplicate removals

Basic unit of exchange is entire message

Allows asynchronous transaction

Three classes of transaction services Class 0: Unreliable one-way requests

Class 1: Reliable one-way requests

Class 2: Reliable two-way request-reply transactions

Based on industry-standard Transport Layer Security (TLS) protocol

Provides Transport layer security between WAP client & WAP Gateway/Proxy

WTLS can be used with both connectionless & connection oriented mode.

Optimized for use over narrow-band communication channels

Features:

◦ Data integrity

◦ Privacy

◦ Authentication

◦ Denial-of-service protection

Provides services and common interface to the upper layer

protocols and hence they function independent of the underlying

wireless network.

Services offered are

oApplication addressing by port numbers

ooptional segmentation and reassembly

ooptional error detection

The WAP datagram protocol (WDP) is the Transport layer that sends

and receives messages via any available bearer network, including

SMS, USSD, CSD, CDPD, IS–136 packet data, and GPRS.

Differing levels of quality of service with respect to

throughput, error rate, and delays

WAP protocols are designed to compensate for or

tolerate these varying levels of service :

o Short Message Service(SMS)

o Circuit Switched Data (CSD)

o Unstructured Supplementary Services Data (USSD)

o General Packet Radio Service(GPRS)

WAP Introduction




Accessing Internet from mobile phones

Application to locate WAP customer geographically

Playing Games from mobile devices over wireless devices

Corporate Applications: Sales force automation where sales people

use their WAP enabled handsets to get instant, direct access to the

latest pricing, latest news, competitive information any time,

anywhere.

Online Services:

o Banking: Users can get their current balance, transfer funds

between accounts and receive fax of a mini-statement.

o Electronic Commerce: Subscribers can use their handset just like

their PC to purchase products and services over the Web.

Tele services

Prepaid Services: With a WAP-enabled phone, prepaid

subscribers can see their current balance with the press of a button.

By pressing another button, they can also recharge their account by

entering a credit card or voucher number into the handset.

Personal Productivity

Email: Using WAP users can keep track of their email right from

their handset.

- Others include: Interactive Chat,Auctions,Games

Most modern mobile devices support WAP

Real time send/receive data

Multiplatform functionality

open standard, vendor independent

network-standard independent

transport mechanism–optimized for wireless data bearers

Easy to write a program and control of web page appearance

application downloaded from the server, enabling fast service

creation and introduction, as opposed to embedded software

Low speed, security and very small user interface

Not very familiar to other users

Small screens: For web phones, there's an incredibly small viewing area; palmtops are barely better.

Speed of access: All devices have slow access.

Business model is expensive

Third party is included

Lack of user habit: It takes some patience and overcoming the learning curve to get the hang of it -- connecting, putting in an address, typing. Users just aren't used to the idea and protocol yet.

Date post:	04-Dec-2021
Category:	Documents
Upload:	others
View:	1 times
Download:	0 times

SNJB’s KBJ COE, Chandwad

Documents