Tutorial at IEEE 802 LMSC Plenary Session, Dallas, TX, USA, Nov. 13, 2006 (with W. Steven Conner, Intel Corp., Jan Kruys, Cisco Systems, and Juan Carlos Zuniga, InterDigital Comm. Corp.).
Protection Technique for Complex Distribution Smart Grid Using Wireless Token...Power System Operation
Distributed generation is expected to increase sharply
as more and more renewable are integrated to power system with
the realization of smart grid, consequently complex distribution
smart grid is given. The traditional protection devices cannot
be able to protect complex power system configuration due to
many fault current loops will feed the fault point. Relays based on
standalone decisions cannot provide reliable and correct action
when used on a complex distribution system. This paper proposes
new protection philosophy using wireless technology. Data
sharing among relays to obtain reliable and accurate decision are
introduced. Wireless Token Ring Protocol (WTRP) as a wireless
local area network (LAN) protocol inspired by the IEEE 802.4
Token Bus Protocol is used for data sharing. WTRP is selected
to improve efficiency by reducing the number of retransmissions
due to collisions. WTRP architecture and protocol are described
to verify operation. MATLAB simulation program is used to
simulate the data exchange protocol between relays in a ring for
a specified amount of time.
Introduction to Wireless Local Area Networks (WLANs). Cover IEEE 802.11a, 802.11b, 802.11g, 802.11n, 802.11i, 802.11x, and deployment & security issues
Introduction to Embedded Systems
Embedded system – classification, Hardware Components of an Embedded system.
Microcontrollers 8051 – Introduction, Architecture, Memory Organization, Instruction Set –
Programming.
Tutorial at IEEE 802 LMSC Plenary Session, Dallas, TX, USA, Nov. 13, 2006 (with W. Steven Conner, Intel Corp., Jan Kruys, Cisco Systems, and Juan Carlos Zuniga, InterDigital Comm. Corp.).
Protection Technique for Complex Distribution Smart Grid Using Wireless Token...Power System Operation
Distributed generation is expected to increase sharply
as more and more renewable are integrated to power system with
the realization of smart grid, consequently complex distribution
smart grid is given. The traditional protection devices cannot
be able to protect complex power system configuration due to
many fault current loops will feed the fault point. Relays based on
standalone decisions cannot provide reliable and correct action
when used on a complex distribution system. This paper proposes
new protection philosophy using wireless technology. Data
sharing among relays to obtain reliable and accurate decision are
introduced. Wireless Token Ring Protocol (WTRP) as a wireless
local area network (LAN) protocol inspired by the IEEE 802.4
Token Bus Protocol is used for data sharing. WTRP is selected
to improve efficiency by reducing the number of retransmissions
due to collisions. WTRP architecture and protocol are described
to verify operation. MATLAB simulation program is used to
simulate the data exchange protocol between relays in a ring for
a specified amount of time.
Introduction to Wireless Local Area Networks (WLANs). Cover IEEE 802.11a, 802.11b, 802.11g, 802.11n, 802.11i, 802.11x, and deployment & security issues
Introduction to Embedded Systems
Embedded system – classification, Hardware Components of an Embedded system.
Microcontrollers 8051 – Introduction, Architecture, Memory Organization, Instruction Set –
Programming.
Analysis and design of algorithms part 3Deepak John
Graphs and graph traversals. Strongly connected components of a Directed graph. Biconnected components of an undirected graph.
Transitive closure of a Binary relation. Warshalls algorithm for Transitive closure. All pair shortest path in graphs. Dynamic programming. Constructing optimal binary search trees.
BER PERFORMANCE ANALYSIS FOR WIMAX PHY LAYER UNDER DIFFERENT CHANNEL CONDITIONSijistjournal
This paper gives an introduction on the IEEE 802.16 standard – WIMAX or Worldwide Interoperability for Microwave Access. The different parts give details on the architectural specifications of WiMAX networks and also on the working principle of WiMAX networks including its services provided. It also provides brief descriptions on its salient features of this technology and how it benefits the networking industry. A brief outline of the basic building blocks or equipment of WiMAX architecture is also provided. This paper also evaluates the simulation performance of IEEE 802.16 OFDM PHY layer. The Stanford University Interim (SUI) channel model under varying parameters is selected for the wireless channel in the simulation. The performance measurements and analysis was done in simulation developed in MATLAB.
BER PERFORMANCE ANALYSIS FOR WIMAX PHY LAYER UNDER DIFFERENT CHANNEL CONDITIONSijistjournal
This paper gives an introduction on the IEEE 802.16 standard – WIMAX or Worldwide Interoperability for
Microwave Access. The different parts give details on the architectural specifications of WiMAX networks
and also on the working principle of WiMAX networks including its services provided. It also provides brief
descriptions on its salient features of this technology and how it benefits the networking industry. A brief
outline of the basic building blocks or equipment of WiMAX architecture is also provided. This paper also
evaluates the simulation performance of IEEE 802.16 OFDM PHY layer. The Stanford University Interim
(SUI) channel model under varying parameters is selected for the wireless channel in the simulation. The
performance measurements and analysis was done in simulation developed in MATLAB.
UNIT II
WIRELESS NETWORKS
Wireless LAN – IEEE 802.11 Standards – Architecture – Services – Mobile Ad hoc Networks- WiFi and WiMAX - Wireless Local Loop
These ppt are the part 2 of mobile computing concepts. These ppt defines the following things
Wireless Networking
Wireless LAN Overview: IEEE 802.11
Wireless applications
Data Broadcasting
Bluetooth
TCP over wireless
Mobile IP
WAP: Architecture, protocol stack, application
environment, applications.
These slides explain the Protocol Framework for 5G mmWave Backhaul Network, as a part of a project presentation for the course Telecom Architecture at Northeastern University.
Register Organization of 8086, Architecture, Signal Description of 8086, Physical Memory
Organization, General Bus Operation, I/O Addressing Capability, Special Processor Activities,
Minimum Mode 8086 System and Timings, Maximum Mode 8086 System and Timings.
Addressing Modes of 8086.
Machine Language Instruction Formats – Instruction Set of 8086-Data transfer
instructions,Arithmetic and Logic instructions,Branch instructions,Loop instructions,Processor
Control instructions,Flag Manipulation instructions,Shift and Rotate instructions,String
instructions, Assembler Directives and operators,Example Programs,Introduction to Stack,
STACK Structure of 8086, Interrupts and Interrupt Service Routines, Interrupt Cycle of 8086,
Non-Maskable and Maskable Interrupts, Interrupt Programming, MACROS.
Network Security: Authentication Applications, Electronic Mail Security, IP Security, Web
Security, System Security: Intruders, Malicious Software, Firewalls
Network Security: Authentication Applications, Electronic Mail Security, IP Security, Web
Security, System Security: Intruders, Malicious Software, Firewalls
Key Management, Diffie-Hellman Key Exchange, Elliptic Curve Arithmetic, Elliptic Curve
Cryptography, Message Authentication and Hash Functions, Hash and MAC Algorithms
Digital Signatures and Authentication Protocols
Key Management, Diffie-Hellman Key Exchange, Elliptic Curve Arithmetic, Elliptic Curve
Cryptography, Message Authentication and Hash Functions, Hash and MAC Algorithms
Digital Signatures and Authentication Protocols
Registers - Serial in serial out, Serial in Parallel out, Parallel in serial out, Parallel in Parallel
out registers, Bidirectional shift registers, universal shift registers.
Counters - Synchronous and asynchronous counters, UP/DOWN counters, Modulo-N
Counters, Cascaded counter, Programmable counter, Counters using shift registers, application
of counters.
Advanced Encryption Standard, Multiple Encryption and Triple DES, Block Cipher Modes of
operation, Stream Ciphers and RC4, Confidentiality using Symmetric Encryption, Introduction
to Number Theory: Prime Numbers, Fermat’s and Euler’s Theorems, Testing for Primality, The
Chinese Remainder Theorem, Discrete Logarithms, Public-Key Cryptography and RSA
Advanced Encryption Standard, Multiple Encryption and Triple DES, Block Cipher Modes of
operation, Stream Ciphers and RC4, Confidentiality using Symmetric Encryption, Introduction
to Number Theory: Prime Numbers, Fermat’s and Euler’s Theorems, Testing for Primality, The
Chinese Remainder Theorem, Discrete Logarithms, Public-Key Cryptography and RSA
Introduction: OSI Security Architecture, Security attacks, ,Security Services, Security
Mechanisms, Model for Network Security, Fundamentals of Abstract Algebra : Groups, Rings,
Fields, Modular Arithmetic, Euclidean Algorithm, Finite Fields of the form GF(p),Polynomial
Arithmetic, Finite Fields of the form GF(2n),Classical Encryption techniques, Block Ciphers and
Data Encryption Standard.
Introduction: OSI Security Architecture, Security attacks, ,Security Services, Security
Mechanisms, Model for Network Security, Fundamentals of Abstract Algebra : Groups, Rings,
Fields, Modular Arithmetic, Euclidean Algorithm, Finite Fields of the form GF(p),Polynomial
Arithmetic, Finite Fields of the form GF(2n),Classical Encryption techniques, Block Ciphers and
Data Encryption Standard.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
1. MODULE 3 MCA-402 Computer Networks ADMN 2012-‘15
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WIRELESS LAN
Is a wireless local area network that uses radio waves as its carrier
Advantages
very flexible within the reception area
Ad-hoc networks without previous planning possible
(almost) no wiring difficulties
More robust against disasters like, e.g., earthquakes, fire - or users pulling a plug...
Disadvantages
typically very low bandwidth (1-10 Mbit/s)
products have to follow many national restrictions
A wireless LAN is based on a cellular architecture where the system is subdivided into cells, where each
cell (called Base Service Set or BSS*) is controlled by a Base station (called Access point or AP).
key application areas:
i. LAN extension
ii. cross-building interconnect
iii. nomadic access
iv. ad hoc networking
i. LAN Extension
Wireless LAN will be linked into a wired LAN on the same premises.
Fig 3.1 Single cell LAN extension
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In a single-cell wireless LAN all of the wireless end systems are within range of a single control
module.
Fig 3.2 Multi cell LAN extension
In a multiple-cell wireless LAN, there are multiple control modules interconnected by a wired
LAN. Each control module supports a number of wireless end systems within its transmission range. For
example, with an infrared LAN, transmission is limited to a single room; therefore, one cell is needed for
each room in an office building that requires wireless support.
ii. Cross-Building Interconnect
connect LANs in nearby buildings
point-to-point wireless link
Devices connected are typically bridges or routers.
Used where cable connection not possible (e.g. across a street)
iii. Nomadic Access
Wireless link between LAN hub and mobile data terminal equipped with antenna
also useful in extended environment such as campus or cluster of buildings
users move around with portable computers
iv. Ad Hoc Networking
Temporary peer-to-peer network set up to meet immediate need
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Fig 3.3 Ad-hoc network
WIRELESS LAN REQUIREMENTS
throughput - efficient use wireless medium
no of nodes - hundreds of nodes across multiple cells
connection to backbone LAN - using control modules
service area - 100 to 300 m
low power consumption - for long battery life on mobiles
transmission robustness and security
license-free operation
handoff/roaming
dynamic configuration - aaddition, deletion, and relocation of end systems without disruption to
users
WIRELESS LAN TECHNOLOGY
Generally categorized according to the transmission technique that is used. They are:
i. Infrared (IR) LANs
ii. Spread spectrum LANs
iii. Narrowband microwave
i. Infrared LANs
constructed using infrared portion of spectrum
strengths
spectrum virtually unlimited hence high rates possible
unregulated spectrum
infrared shares some properties of visible light
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i. reflection covers room, walls isolate networks
inexpensive and simple
weaknesses
background radiation, e.g. ssunlight, indoor lighting
power limited by concerns for eye safety and power consumption
Transmission Techniques
directed-beam IR
point-to-point links
range depends on power and focusing
for indoor use can set up token ring LAN
omnidirectional
single base station with line of sight to other stations
acts as a multiport repeater
other stations use directional beam to it
diffused configuration
stations focused / aimed at diffusely reflecting ceiling
ii. Spread Spectrum LAN Configuration
usually use multiple-cell arrangement
Adjacent cells use different center frequencies.
configurations:
hub
i. connected to wired LAN
ii. connect to stations on wired LAN and in other cells
iii. may do automatic handoff
peer-to-peer
i. no hub
ii. MAC algorithm such as CSMA used to control access
iii. for ad hoc LANs
Transmission Issue
Three microwave bands have been set aside by FCC which doesn’t need a license if the
equipment’s operates under 1W power
They are:
902-928 MHz (915 MHz band)-Industrial Band
2.4-2.4835 GHz (2.4 GHz band)-Scientific Band
5. MODULE 3 MCA-402 Computer Networks ADMN 2012-‘15
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5.725-5.825 GHz (5.8 GHz band)- Medical Band
Commonly known as ISM band ,it is used by Wireless LAN with spread spectrum technology
iii. Narrowband Microwave LANs
Use of a microwave radio frequency band for signal transmission
i. Licensed
ii. Unlicensed
1. Licensed Narrowband RF
Microwave radio frequencies are licensed within specific geographic areas to avoid potential
interference.
Each geographic area has a radius of 28 km and can contain five licenses, with each license
covering two frequencies.
Uses cell configuration(18GHz)
One advantage of the licensed narrowband LAN is that it guarantees interference-free
communication
2. Unlicensed Narrowband RF
Radio LAN introduced narrowband wireless LAN in 1995 which uses the unlicensed ISM
spectrum
Used at low power (0.5 watts or less)
Operates at 10 Mbps in the 5.8-GHz band
Range = 50 m to 100 m
The RadioLAN product makes use of a peer-to-peer configuration.
RadioLAN product automatically elects one node as the Dynamic Master.
IEEE 802.11
IEEE has defined the specifications for a wireless LAN, called IEEE 802.11, which covers the
physical and data link layers.
Defines standard for WLANs using the following four technologies
Frequency Hopping Spread Spectrum (FHSS)
Direct Sequence Spread Spectrum (DSSS)
Infrared (IR)
Orthogonal Frequency Division Multiplexing (OFDM)
Versions: 802.11a, 802.11b, 802.11g, 802.11e, 802.11f, 802.11i
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802.11 - ARCHITECTURE
Fig 3.4 a. Ad-hoc network b. Infrastructure network
Station (STA)
terminal with access mechanisms to the wireless medium and radio contact to the access
point
Basic Service Set (BSS)
group of stations using the same radio frequency
Access Point
station integrated into the wireless LAN and the distribution system
Portal
bridge to other (wired) networks
Distribution System
interconnection network to form one logical network
802.11 Services
a) Distribution of Messages
Distribution service (DS):Used to exchange MAC frames from station in one BSS to station in
another BSS
Integration service: Transfer of data between station on IEEE 802.11 LAN and station on
integrated IEEE 802.x LAN
b) Association Related Services
Association: Establishes initial association between station and AP.
Re-association: Enables transfer of association from one AP to another, allowing station to move
from one BSS to another.
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Disassociation: Association termination notice from station or AP
c) Access and Privacy Services
Authentication: Establishes identity of stations to each other.
De-authentication: Invoked when existing authentication is terminated
Privacy: Prevents message contents from being read by unintended recipient
802.11 PROTOCOL STACK
Fig 3.5 802.11 protocol stack
Medium Access Control
The Medium Access Control sub layer of wireless local area network is more complex than MAC sub
layer of wired local area networks.
MAC layer covers three functional areas
reliable data delivery
access control
Security
i. Reliable Data Delivery
Loss of frames due to noise, interference, and propagation effects.
To ensure reliable data delivery IEEE 802.11 includes a frame exchange protocol.
Two frame exchange
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Source station transmits data
Destination responds with acknowledgment (ACK)
If source doesn’t receive ACK, it retransmits frame
Four frame exchange for enhanced reliability
Source issues request to send (RTS)
Destination responds with clear to send (CTS)
Source transmits data
Destination responds with ACK
The RTS alerts all stations that are within reception range of the source that an exchange is under
way
Similarly, the CTS alerts all stations that are within reception range of the destination that an
exchange is under way
ii. Access Control
Medium access control is based on distributed control and centralized control.
Uses a MAC algorithm called DFWMAC (distributed foundation wireless MAC).
It provides a distributed access control mechanism with an optional centralized control.
IEEE 802.11 defines two MAC sub layers: the distributed coordination function (DCF) & Point
coordination Function (PCF).
1. Distributed Coordination Function(DCF)
The lower sub layer of the MAC layer.
DCF sub layer uses CSMA /CA
if station has frame to send it listens to medium
if medium idle, station may transmit
else waits until current transmission complete
To ensure the smooth and fair functioning of CSMA, the MAC frame transmissions are separated
by a time gap called IFS.
2. Point Coordination Function (PCF)
polling by centralized polling master (point coordinator)
uses PIFS when issuing polls
point coordinator polls in round-robin to stations configured for polling
when poll issued, polled station may respond using SIFS
if point coordinator receives response, it issues another poll using PIFS
if no response during expected turnaround time, coordinator issues poll
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3. SIFS (short IFS)
The shortest IFS, used for all immediate response actions, like Acknowledgment, and Clear to send
(CTS) Frames
Fig 3.6 Access control
Following illustrates the use of these time values. Consider first the SIFS. Any station using SIFS
to determine transmission opportunity has, in effect, the highest priority, because it will always gain
access in preference to a station waiting an amount of time equal to PIFS or DIFS.
Fig 3.7 basic access method
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802.11 MAC Frame Format
Fig 3.7 IEEE 802.3 MAC frame
Control Frames
Power Save-Poll (PS-Poll)
Request to Send (RTS)
Clear to Send (CTS)
Acknowledgment (ACK)
Contention-Free (CF)-end
CF-End + CF-Ack
Management Frames
used to manage communications between stations and Aps
such as management of associations
requests, response, reassociation, dissociation, and authentication
Data Frames
eight data frame subtypes, in two groups
1. Data Carrying
carry upper-level data
2. Not Data Carrying
do not carry user data
Null Function
carries no data, polls, or acknowledgments
carries power mgmt. bit in frame control field to AP
indicates station is changing to low-power state
11. MODULE 3 MCA-402 Computer Networks ADMN 2012-‘15
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802.11 Addressing
There are four address fields, each 6 bytes long.
The IEEE 802.11 addressing mechanism specifies four cases, defined by the value of the two flags
in the FC field, To DS and From DS.
The interpretation of the four addresses (address 1 to address 4) in the MAC frame depends on the
value of these flags
Fig 3.8 addressing in 802.11 MAC
802.11 Physical Layer
The PHY is the interface between the MAC and wireless media, which transmits and receives data
frames over a shared wireless medium.
The physical layer is further subdivided into sub layers:
Physical Layer Convergence Procedure (PLCP) sub layer:
Reformats data received from MAC layer into frame that PMD sub layer can transmit
Physical Medium Dependent (PMD) Sub layer:
Takes the binary bits of information from PLCP-PDU (PPDU) and transform them into RF signals
defines method for transmitting and receiving data
Three physical media are defined in the original 802.11 standard:
Direct sequence spread spectrum (DSSS)
Frequency-hopping spread spectrum (FHSS)
Infrared
802.11 DSSS
Operating in the 2.4-GHz ISM band, at data rates of 1 Mbps and 2 Mbps.
Up to three non-overlapping channels, each with a data rate of 1 Mbps or 2 Mbps, can be used in
the DSSS scheme.
Each channel has a bandwidth of 5 MHz
The encoding scheme that is used is DBPSK (differential binary phase shift keying) for the 1 Mbps
rate and DQPSK(differential Quadrature phase shift keying )for the 2 Mbps rate.
12. MODULE 3 MCA-402 Computer Networks ADMN 2012-‘15
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802.11 FHSS
FHSS system makes use of multiple channels,
Data transmission over the media is controlled by the FHSS PMD sub layer as directed by the
FHSS PLCP sub layer.
PMD takes the binary bits of and transforms them into RF signals for the wireless media by using
carrier modulation and FHSS technique
802.11b HR-DSSS
The IEEE 802.11b PHY is one of the PHY layer extensions of IEEE 802.11 and is referred to as
high rate direct sequence spread spectrum (HR/DSSS).
Providing data rates of 5.5 and 11 Mbps.
IEEE 802.11b defines two physical-layer frame formats, which differ only in the length of the
preamble
802.11a OFDM
Makes use of the frequency band called the Universal Networking Information Infrastructure
(UNII), which is divided into three parts.
UNII-1 band is intended for indoor use
UNII-2 band be used either indoor or outdoor,
UNII-3 band is for outdoor use.
The IEEE 802.11a PHY adopts orthogonal frequency division multiplexing (OFDM) instead of
spread spectrum techniques
OFDM splits a single high-speed digital signal into several slower signals running in parallel.
Provides rates of 6, 9 , 12, 18, 24, 36, 48, 54 Mbps
802.11g OFDM
Extends data rates above 20 Mbps, up to 54 Mbps.
Operates in the 2.4-GHz.
Offers a wider array of data rate and modulation schemes.
Provides compatibility with 802.11 by specifying the same modulation and framing schemes as
these standards for 1, 2, 5.5, and 11 Mbps.
BLUE TOOTH
IEEE 802.15
Is a wireless LAN technology using short-range radio links, intended to replace the cable(s)
connecting portable and/or fixed electronic devices.
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Is an ad hoc network where devices can automatically find each other, establish connections, and
discover what they can do for each other.
Range 10-100 metres.
Features are robustness, low complexity, low power and low cost.
uses a 2.4-GHz ISM band divided into 79 channels of 1 MHz each
A Bluetooth device has a built-in short-range radio transmitter.
It uses Frequency Hop Spread Spectrum (FHSS) to avoid any interference.
Applications
Automatic synchronization between mobile and stationary devices
Connecting mobile users to the internet using Bluetooth-enabled wire-bound connection ports
Dynamic creation of private networks
Types of Bluetooth Wireless Technology
Depending on the power consumption and range of the device, there are 3 Bluetooth Classes as:
1. Class 1: Max Power – 100mW ; Range – 100 m
2. Class 2: Max Power – 2.5mW ; Range – 10 m
3. Class 3: Max Power – 1mW ; Range – 1 m
Protocol Architecture
Bluetooth is a layered protocol architecture
Core protocols
Cable replacement and telephony control protocols
Adopted protocols
Core protocols
Radio
Baseband
Link manager protocol (LMP)
Logical link control and adaptation protocol (L2CAP)
Service discovery protocol (SDP)
Cable replacement protocol
RFCOMM
Telephony control protocol
Telephony control specification – binary (TCS BIN)
Adopted protocols
TCP/UDP/IP
OBEX
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WAE/WAP
Fig 3.9 Bluetooth protocol architecture
Radio Layer
The bottom layer in protocol stack, equivalent to the physical layer of the Internet model.
It deals with radio transmission and modulation.
The Radio layer defines the requirements for a Bluetooth transceiver operating in the 2.4 GHz ISM
band.
Divided into 79 channels of 1 MHz each.
Support data rate: 1Mbps (Basic Rate) / 3 Mbps (Enhanced Data Rate).
Uses a technique called frequency hopping, for establishing radio links with other Bluetooth
devices
Baseband layer
Is roughly equivalent to the MAC sub layer in LANs.
It is responsible for constructing, encoding and decoding packets, and managing error correction,
encrypting and decrypting for secure communication etc..
The primary and secondary communicate with each other using time slots.
Two types of links can be established between primary and secondary:
Synchronous connection-oriented (SCO) links:
Used when avoiding latency (delay in data delivery) is more important than
15. MODULE 3 MCA-402 Computer Networks ADMN 2012-‘15
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integrity (error- free delivery).
Used for voice transmission.
Asynchronous connectionless (ACL) links:
Used when data integrity is more important than avoiding latency.
Used for data transmission.
L2CAP
The Logical Link Control and Adaptation Protocol, is roughly equivalent to the LLC sub layer in
LANs.
Used for data exchange on an ACL link; SCO channels do not use L2CAP.
This layer has four major functions:
• First, it accepts packets of up to 64 KB from the upper layers and breaks them into frames for
transmission.
• Second, it handles the multiplexing and de-multiplexing of multiple packet sources.
• Third, L2CAP handles Segmentation and reassembly
• Finally, L2CAP enforces quality of service requirements between multiple links.
Audio: interfaces directly with the baseband. Each voice connection is over a 64Kbps.uses PCM
encoding.
Host Controller Interface: provides a uniform method of access to the baseband, control registers, etc
through USB, PCI, or UART.
Service Discover Protocol (SDP): protocol of locating services provided by a Bluetooth device.
Telephony Control Specification (TCS): defines the call control signaling for the establishment of
speech and data calls between Bluetooth devices.
RFCOMM: provides emulation of serial links (RS232). Up to 60 connections
Bluetooth Topology
Bluetooth defines two types of network topology:
Piconet
Scatternet
PICONET
Known as small net, have up to eight stations.
One primary, the rest are secondary.
Communication can be one-to-one or one-to-many.
Each of the active slaves has an assigned 3-bit Active Member address.
An additional eight secondary's can be in the “parked state.
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A secondary in a “parked state” is synchronised with the primary but cannot take part in
communication until it is moved from the “parked state”
Fig 3.10 Piconet
Scatternet
Formed by the combinations of piconet.
A secondary station in one piconet can be the primary in another piconet.
This station can receive messages from the primary in the first piconet (as a secondary) and acting
as a primary, deliver them to secondary’s in the second piconet .
Fig 3.11 scatternet
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States of a Bluetooth Device
ACTIVE (connected/transmit): the device is uniquely identified by a 3bits AM_ADDR and is fully
participating.
SNIFF state: participates in the piconet only within the SNIFF interval.
HOLD state: no data transfer, master can put slaves on HOLD state.
PARK state (low-power): releases AM_ADDR but stays synchronized with master
Fig 3.12 Bluetooth device states
Bluetooth Link Security
Elements:
Authentication – verify claimed identity
Encryption – privacy
Key management and usage
Security algorithm parameters:
Unit address
Secret authentication key (128 bits key)
Secret privacy key (4-128 bits secret key)
Random number
VIRTUAL LAN
A virtual local area network (VLAN) is a logical group of workstations, servers and network
devices that appear to be on the same LAN despite their geographical distribution.
All workstations and servers used by a particular workgroup share the same VLAN, regardless of
the physical connection or location.
The group membership in VLANs is defined by software, not hardware.
A VLAN is a broadcast domain created by one or more switches.
802.1Q
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Fig 3.13 network without VLAN and with VLAN
VLAN Membership
Each switch port could be assigned to a different VLAN.
Ports assigned to the same VLAN share broadcasts.
Ports that do not belong to that VLAN do not share these broadcasts.
VLAN operation
1. VLANs are assigned on the switch port. There is no “VLAN” assignment done on the host
(usually).
2. In order for a host to be a part of that VLAN, it must be assigned an IP address that belongs to the
proper subnet. Remember: VLAN = Subnet.
3. Assigning a host to the correct VLAN is a 2-step process:
1. Connect the host to the correct port on the switch.
2. Assign to the host the correct IP address depending on the VLAN membership
1. Static VLAN
Are called port-based and port-centric membership VLANs.
Ports on a switch are manually assigned to a VLAN.
This is the most common method of assigning ports to VLANs.
As a device enters the network, it automatically assumes the VLAN membership of the port to
which it is attached.
2. Dynamic VLAN
Allow membership based on the MAC address of the device connected to the switch port.
As a device enters the network, it queries a database within the switch for a VLAN membership.
Membership is configured using a special server called a VLAN Membership Policy Server
(VMPS).
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Configuration
Network administrators are responsible for configuring VLANs both manually and statically
Fig 3.14 VLAN configuration
Communication
Each switch must know about which station belongs to which VLAN and the membership of
stations connected to other switches.
Three methods have been devised for this purpose:
i. Table maintenance
ii. Frame tagging
iii. Time-division multiplexing.
i. Table Maintenance
When a station sends a broadcast frame to its group members, the switch creates an entry in a table
and records station membership.
The switches send their tables to one another periodically for updating.
ii. Frame Tagging
When a frame is traveling between switches, an extra header is added to the MAC frame to
define the destination VLAN.
The frame tag is used by the receiving switches to determine the VLANs to be receiving the
broadcast message.
iii. Time-Division Multiplexing (TDM)
the connection (trunk) between switches is divided into timeshared channels
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IEEE 802.1Q: Features
Allows up to 4095 VLANs
Allows port based and MAC address based,
Upward compatible with existing VLAN-unware hubs and bridges
Supports both shared-media and switched LANs.
Retains plug and play mode of current LAN bridges.
Allows priority associated with each VLAN.
Supports static and dynamic configurations for each VLAN
Advantages & Disadvantage
Disadvantage:
Costly
Software based
Human labor to program
Depending on variety switches
Management complexity
Advantages:
More Security
Ease of administration
Broadcast control
Reduction in network traffic