This document provides an overview of wireless LANs, including their applications and technology. It discusses the four main application areas of wireless LANs: LAN extension, cross-building interconnect, nomadic access, and ad hoc networks. It also covers wireless LAN requirements and the two main technologies: infrared LANs and spread spectrum LANs. Finally, it summarizes the IEEE 802.11 standard for wireless LANs, including its architecture, services, and medium access control sublayer.
Wireless LAN technologies can be categorized based on their transmission technique. Infrared LANs use infrared light which does not penetrate walls but avoids interference. Spread spectrum LANs operate in unlicensed bands and can be configured in a hub or ad hoc topology. Narrowband microwave LANs can be licensed or unlicensed, with licensed providing guaranteed interference-free communication but requiring fees.
Wireless LANs allow for wireless transmission of data within a local area network (LAN). The document discusses:
1. Wireless LANs were initially more expensive and had lower data rates than wired LANs, but these issues have been addressed and wireless LAN popularity has grown.
2. Wireless LANs are commonly used to extend existing wired LANs by avoiding cable installation, and to provide connectivity in areas not suited for wired LANs like large open spaces.
3. The IEEE 802.11 standard defines the media access control (MAC) and physical layers for wireless LANs. It uses carrier sense multiple access with collision avoidance (CSMA/CA) for distributed
This document discusses wireless local area networks (WLANs). It describes how WLANs use wireless transmission to connect devices within a local area, avoiding the need for wired networking. It covers different types of WLAN configurations including single-cell, multi-cell, infrastructure and ad-hoc networks. It also discusses wireless networking technologies like infrared, spread spectrum and microwave transmission and compares their strengths and weaknesses. Finally, it examines the IEEE 802.11 wireless networking standard and its media access control protocols.
This chapter discusses wireless LANs, including their growth in popularity as issues like high prices and licensing requirements have been addressed. Wireless LANs can be used to extend a wired LAN by replacing cabling, though replacing the wired LAN entirely has not occurred. Wireless LANs are used in environments like open areas, historical buildings, and small offices where wired LANs are not economical. Key technologies discussed include infrared and spread spectrum LANs. The IEEE 802.11 standard defines the basic service set and extended service set for wireless LAN configuration and services.
This document discusses wireless local area networks (WLANs). It describes how WLANs use wireless transmission to connect devices within a local area, avoiding the need for wired networking. It covers different types of WLAN configurations including single-cell, multi-cell, infrastructure and ad-hoc networks. It also discusses wireless networking technologies like infrared, spread spectrum and microwave transmission and compares their strengths and weaknesses. Finally, it examines the IEEE 802.11 wireless networking standard and its use of distributed coordination function (DCF) and point coordination function (PCF) for medium access control.
WLAN allows devices to connect to a local area network without being physically connected with cables. It uses wireless transmission through radio waves or infrared instead of wires or cables. Typical WLAN configurations include using an access point or wireless router to connect multiple devices within a small area. While WLAN provides flexibility compared to wired networks, it also has limitations such as lower bandwidth and potential security issues. Common wireless technologies used in WLAN include infrared, microwave radio using spread spectrum techniques like FHSS and DSSS, and narrowband radio transmission. WLAN finds applications in situations that require mobile access or temporary networking within an organization.
This document outlines the course objectives, syllabus, and outcomes for the course EC8702 Ad Hoc and Wireless Sensor Networks. The course aims to teach students about ad hoc network and sensor network fundamentals, routing protocols, sensor network architecture and design issues, transport layer and security issues, and sensor network platforms and tools. The syllabus covers topics like ad hoc network routing protocols, sensor network introductions and architectures, networking concepts and protocols, security issues, and sensor network platforms. Upon completing the course, students will gain knowledge of ad hoc and sensor networks and be able to apply this to identify suitable protocols and address issues in these networks.
Overview
WLAN Technologies - Infrared LANs, Spread Spectrum LANs, Narrowband Microwave LANs
IEEE 802.11 – Architecture, protocols, MAC layer, MAC Frame, MAC Management
Infra Red
Wireless LAN technologies can be categorized based on their transmission technique. Infrared LANs use infrared light which does not penetrate walls but avoids interference. Spread spectrum LANs operate in unlicensed bands and can be configured in a hub or ad hoc topology. Narrowband microwave LANs can be licensed or unlicensed, with licensed providing guaranteed interference-free communication but requiring fees.
Wireless LANs allow for wireless transmission of data within a local area network (LAN). The document discusses:
1. Wireless LANs were initially more expensive and had lower data rates than wired LANs, but these issues have been addressed and wireless LAN popularity has grown.
2. Wireless LANs are commonly used to extend existing wired LANs by avoiding cable installation, and to provide connectivity in areas not suited for wired LANs like large open spaces.
3. The IEEE 802.11 standard defines the media access control (MAC) and physical layers for wireless LANs. It uses carrier sense multiple access with collision avoidance (CSMA/CA) for distributed
This document discusses wireless local area networks (WLANs). It describes how WLANs use wireless transmission to connect devices within a local area, avoiding the need for wired networking. It covers different types of WLAN configurations including single-cell, multi-cell, infrastructure and ad-hoc networks. It also discusses wireless networking technologies like infrared, spread spectrum and microwave transmission and compares their strengths and weaknesses. Finally, it examines the IEEE 802.11 wireless networking standard and its media access control protocols.
This chapter discusses wireless LANs, including their growth in popularity as issues like high prices and licensing requirements have been addressed. Wireless LANs can be used to extend a wired LAN by replacing cabling, though replacing the wired LAN entirely has not occurred. Wireless LANs are used in environments like open areas, historical buildings, and small offices where wired LANs are not economical. Key technologies discussed include infrared and spread spectrum LANs. The IEEE 802.11 standard defines the basic service set and extended service set for wireless LAN configuration and services.
This document discusses wireless local area networks (WLANs). It describes how WLANs use wireless transmission to connect devices within a local area, avoiding the need for wired networking. It covers different types of WLAN configurations including single-cell, multi-cell, infrastructure and ad-hoc networks. It also discusses wireless networking technologies like infrared, spread spectrum and microwave transmission and compares their strengths and weaknesses. Finally, it examines the IEEE 802.11 wireless networking standard and its use of distributed coordination function (DCF) and point coordination function (PCF) for medium access control.
WLAN allows devices to connect to a local area network without being physically connected with cables. It uses wireless transmission through radio waves or infrared instead of wires or cables. Typical WLAN configurations include using an access point or wireless router to connect multiple devices within a small area. While WLAN provides flexibility compared to wired networks, it also has limitations such as lower bandwidth and potential security issues. Common wireless technologies used in WLAN include infrared, microwave radio using spread spectrum techniques like FHSS and DSSS, and narrowband radio transmission. WLAN finds applications in situations that require mobile access or temporary networking within an organization.
This document outlines the course objectives, syllabus, and outcomes for the course EC8702 Ad Hoc and Wireless Sensor Networks. The course aims to teach students about ad hoc network and sensor network fundamentals, routing protocols, sensor network architecture and design issues, transport layer and security issues, and sensor network platforms and tools. The syllabus covers topics like ad hoc network routing protocols, sensor network introductions and architectures, networking concepts and protocols, security issues, and sensor network platforms. Upon completing the course, students will gain knowledge of ad hoc and sensor networks and be able to apply this to identify suitable protocols and address issues in these networks.
Overview
WLAN Technologies - Infrared LANs, Spread Spectrum LANs, Narrowband Microwave LANs
IEEE 802.11 – Architecture, protocols, MAC layer, MAC Frame, MAC Management
Infra Red
The document provides definitions and explanations of various communication and network concepts. It discusses networking devices like modems, switches, and hubs. It describes different types of networks including LAN, MAN, WAN, and PAN. It also covers networking protocols such as TCP/IP, FTP, and HTTPS. Finally, it discusses network security concepts like firewalls, cyber laws, and different types of cyber attacks.
This document provides an overview of wireless networks and the IEEE 802.11 standards. It discusses wireless LAN technologies including IEEE 802.11, HiperLAN, Bluetooth, and various amendments. It describes the infrastructure and ad-hoc modes of wireless LANs. It also summarizes key standards such as 802.11a, 802.11b, their architectures, protocols, and parameters. Finally, it provides details on the HiperLAN standard developed by ETSI for wireless local area networks in Europe.
The document discusses wireless local area networks (WLANs) and their advantages over wired networks, including mobility, ease of installation, flexibility, and reduced costs. It describes various WLAN configurations including peer-to-peer networks, client/access point networks, and networks using multiple access points or extension points. The document also covers WLAN standards, hardware components, connection processes, capacity, and technologies used including spread spectrum techniques like direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS).
Types o Wireless Networks in computer networksPonniS7
Wireless networks provide wireless interfaces to users by supporting bandwidth allocation and error-control functions. There are different types of wireless networks such as wireless local area networks (WLANs), mobile networks, and sensor networks. Each network faces various challenges including lower bandwidth capacity, interference, security issues, and power constraints depending on the network type.
This document provides an overview of computer networking concepts including different network topologies, transmission media, and network components. It defines key networking terms like local area network (LAN), metropolitan area network (MAN), wide area network (WAN), and personal area network (PAN). Different network topologies like bus, star, ring, and mesh are described. Common transmission media include coaxial cable, twisted pair cable, optical fiber, and wireless transmission. Network components such as hubs, switches, routers, bridges, and gateways are also explained.
Wireless LAN (WLAN) allows devices to connect to a local area network through wireless connections. It uses radio frequencies and electromagnetic waves to transmit data without cables. Common wireless standards used include 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac. WLAN provides flexibility and lower installation costs compared to wired LAN, but can have lower quality of service and be subject to interference.
The document provides an overview of wireless distributed antenna systems (DAS) and backhaul antenna systems. It discusses the key components of these systems including antennas, cabling, towers, amplifiers and how they are used to extend wireless coverage both indoors and outdoors. The document also reviews important design considerations for implementing DAS such as conducting a needs analysis, evaluating configurations, and testing installations.
The document provides information on the history and types of wireless LANs and mobile networks. It discusses:
- The early development of wireless technologies from 1971 including ALOHAnet and experimental wireless networks. Standards like IEEE 802.11 were introduced from 1997.
- Types of wireless LANs including infrared, spread spectrum, and narrowband microwave networks. Key standards are also discussed like IEEE 802.11, HiperLAN, Bluetooth, and HomeRF.
- Challenges for wireless networks including improving data rates, addressing security and interference issues, and ensuring system interoperability. Seamless handoff between access points is also discussed.
Ethernet technology and its evolution has seen increasing speeds over time from early Ethernet to today's 400GE. Ethernet standards are developed by IEEE and include elements like interconnect media and network nodes. Common network topologies include point-to-point, bus, and star configurations. As speeds increased standards were developed for Gigabit Ethernet, then 40GE, 100GE, and the emerging 400GE. IPv4 address space is limited but IPv6 provides vastly more addresses; transition strategies include dual stack, 6rd rapid deployment, and large scale NAT to allow continued use of IPv4 while deploying IPv6.
This pesentation explains some topics realated to the computer networking...
Basically we are covering the following areas...
1. Ethernet Technology and its Evolution
2. Wireless Networking Technologies
3. IPv4 and IPv6 Coexistence
This will help the students to get a good idea about Computer Networking field...
advanced metering infrastructure, advanced meter reading, internet of Things, WiMax, LTE, smart meter analytics, smart meter communication technologies, LTE advanced, WiFi, smart meter architectural blueprint
More details: (blog: http://sandyclassic.wordpress.com ,
linkedin: ie.linkedin.com/in/sandepsharma/)
This document provides an overview of communication and network concepts. It discusses the evolution of networking from ARPANET in 1969 to the modern Internet. It describes common network components like switches, routers, and gateways. It also covers different types of networks, topologies, transmission media like twisted pair, coaxial cable, optical fiber and wireless transmission. Network protocols, security concepts, open source software, and types of malware are also summarized.
fundamental of networking course, LAN,WAN,TCP,IPHusseinAwil
This document provides an overview of network fundamentals including network structure, protocols, transmission media, and hardware. It discusses the basic concepts of communications and networking. It describes common network transmission media like coaxial cable, twisted pair, optical fiber, and wireless transmission. It also explains key network hardware like hubs, bridges, routers, switches, and various wide area network technologies. Finally, it distinguishes between local area networks and wide area networks.
The document outlines a presentation on power system communications and smart grid communications. It discusses various wired and wireless communication technologies used in power systems like power line carrier communication, fiber optics, radio systems, and cellular networks. It also covers smart grid communication requirements, infrastructure including home, neighborhood and wide area networks. Standards like IEC 61850 and DNP3 used for information exchange are also summarized.
The document discusses basic networking concepts including LANs, wireless LANs, network hardware, common network media, and Ethernet specifications. It defines a LAN as a group of computers and devices sharing resources within a small geographic area. Wireless LANs transmit over the air using unlicensed frequencies. Common network hardware includes hubs, switches, bridges, routers and network interface cards. Wired networks typically use copper or fiber optic cable, while wireless networks transmit over radio frequencies. The document provides examples of LAN implementations in home and business configurations.
History, Basic concepts of wireless communication, challenges in wireless communication, cellular communication, performance criteria, wireless communication standars, how call is made?
Networking Components,
Types of Network,
Different Protocols used in Network,
Networking Technology(cables & Wires)
Wireless Technology,
Mobile Technology,
Presented by
Yuvashri
Presentation on different modes of data communicationTafadzwa Gonera
This document discusses different modes of data communication, including wired and wireless technologies. It describes protocol models like OSI and TCP/IP that define network layers. Wired technologies covered include coaxial cable, fiber optic cable, and twisted pair cable. Wireless technologies discussed are Bluetooth, WiMAX, infrared, and Wi-Fi. The document provides definitions, diagrams, advantages and disadvantages of each technology discussed.
The document provides an introduction to computer networking concepts. It defines a network as consisting of two or more connected computers that can share resources and information. Networks allow for sharing of hardware, software, data, and centralized administration. There are different types of networks classified by transmission medium (wired vs wireless), size (LAN vs WAN), management method (peer-to-peer vs client/server), and topology (bus, star, ring). Common transmission media include twisted-pair cables, coaxial cables, and fiber-optic cables. LANs are small, local networks while WANs connect multiple LANs over longer distances using technologies like broadband. Client/server networks have dedicated server computers that provide resources to
The document provides definitions and explanations of various communication and network concepts. It discusses networking devices like modems, switches, and hubs. It describes different types of networks including LAN, MAN, WAN, and PAN. It also covers networking protocols such as TCP/IP, FTP, and HTTPS. Finally, it discusses network security concepts like firewalls, cyber laws, and different types of cyber attacks.
This document provides an overview of wireless networks and the IEEE 802.11 standards. It discusses wireless LAN technologies including IEEE 802.11, HiperLAN, Bluetooth, and various amendments. It describes the infrastructure and ad-hoc modes of wireless LANs. It also summarizes key standards such as 802.11a, 802.11b, their architectures, protocols, and parameters. Finally, it provides details on the HiperLAN standard developed by ETSI for wireless local area networks in Europe.
The document discusses wireless local area networks (WLANs) and their advantages over wired networks, including mobility, ease of installation, flexibility, and reduced costs. It describes various WLAN configurations including peer-to-peer networks, client/access point networks, and networks using multiple access points or extension points. The document also covers WLAN standards, hardware components, connection processes, capacity, and technologies used including spread spectrum techniques like direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS).
Types o Wireless Networks in computer networksPonniS7
Wireless networks provide wireless interfaces to users by supporting bandwidth allocation and error-control functions. There are different types of wireless networks such as wireless local area networks (WLANs), mobile networks, and sensor networks. Each network faces various challenges including lower bandwidth capacity, interference, security issues, and power constraints depending on the network type.
This document provides an overview of computer networking concepts including different network topologies, transmission media, and network components. It defines key networking terms like local area network (LAN), metropolitan area network (MAN), wide area network (WAN), and personal area network (PAN). Different network topologies like bus, star, ring, and mesh are described. Common transmission media include coaxial cable, twisted pair cable, optical fiber, and wireless transmission. Network components such as hubs, switches, routers, bridges, and gateways are also explained.
Wireless LAN (WLAN) allows devices to connect to a local area network through wireless connections. It uses radio frequencies and electromagnetic waves to transmit data without cables. Common wireless standards used include 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac. WLAN provides flexibility and lower installation costs compared to wired LAN, but can have lower quality of service and be subject to interference.
The document provides an overview of wireless distributed antenna systems (DAS) and backhaul antenna systems. It discusses the key components of these systems including antennas, cabling, towers, amplifiers and how they are used to extend wireless coverage both indoors and outdoors. The document also reviews important design considerations for implementing DAS such as conducting a needs analysis, evaluating configurations, and testing installations.
The document provides information on the history and types of wireless LANs and mobile networks. It discusses:
- The early development of wireless technologies from 1971 including ALOHAnet and experimental wireless networks. Standards like IEEE 802.11 were introduced from 1997.
- Types of wireless LANs including infrared, spread spectrum, and narrowband microwave networks. Key standards are also discussed like IEEE 802.11, HiperLAN, Bluetooth, and HomeRF.
- Challenges for wireless networks including improving data rates, addressing security and interference issues, and ensuring system interoperability. Seamless handoff between access points is also discussed.
Ethernet technology and its evolution has seen increasing speeds over time from early Ethernet to today's 400GE. Ethernet standards are developed by IEEE and include elements like interconnect media and network nodes. Common network topologies include point-to-point, bus, and star configurations. As speeds increased standards were developed for Gigabit Ethernet, then 40GE, 100GE, and the emerging 400GE. IPv4 address space is limited but IPv6 provides vastly more addresses; transition strategies include dual stack, 6rd rapid deployment, and large scale NAT to allow continued use of IPv4 while deploying IPv6.
This pesentation explains some topics realated to the computer networking...
Basically we are covering the following areas...
1. Ethernet Technology and its Evolution
2. Wireless Networking Technologies
3. IPv4 and IPv6 Coexistence
This will help the students to get a good idea about Computer Networking field...
advanced metering infrastructure, advanced meter reading, internet of Things, WiMax, LTE, smart meter analytics, smart meter communication technologies, LTE advanced, WiFi, smart meter architectural blueprint
More details: (blog: http://sandyclassic.wordpress.com ,
linkedin: ie.linkedin.com/in/sandepsharma/)
This document provides an overview of communication and network concepts. It discusses the evolution of networking from ARPANET in 1969 to the modern Internet. It describes common network components like switches, routers, and gateways. It also covers different types of networks, topologies, transmission media like twisted pair, coaxial cable, optical fiber and wireless transmission. Network protocols, security concepts, open source software, and types of malware are also summarized.
fundamental of networking course, LAN,WAN,TCP,IPHusseinAwil
This document provides an overview of network fundamentals including network structure, protocols, transmission media, and hardware. It discusses the basic concepts of communications and networking. It describes common network transmission media like coaxial cable, twisted pair, optical fiber, and wireless transmission. It also explains key network hardware like hubs, bridges, routers, switches, and various wide area network technologies. Finally, it distinguishes between local area networks and wide area networks.
The document outlines a presentation on power system communications and smart grid communications. It discusses various wired and wireless communication technologies used in power systems like power line carrier communication, fiber optics, radio systems, and cellular networks. It also covers smart grid communication requirements, infrastructure including home, neighborhood and wide area networks. Standards like IEC 61850 and DNP3 used for information exchange are also summarized.
The document discusses basic networking concepts including LANs, wireless LANs, network hardware, common network media, and Ethernet specifications. It defines a LAN as a group of computers and devices sharing resources within a small geographic area. Wireless LANs transmit over the air using unlicensed frequencies. Common network hardware includes hubs, switches, bridges, routers and network interface cards. Wired networks typically use copper or fiber optic cable, while wireless networks transmit over radio frequencies. The document provides examples of LAN implementations in home and business configurations.
History, Basic concepts of wireless communication, challenges in wireless communication, cellular communication, performance criteria, wireless communication standars, how call is made?
Networking Components,
Types of Network,
Different Protocols used in Network,
Networking Technology(cables & Wires)
Wireless Technology,
Mobile Technology,
Presented by
Yuvashri
Presentation on different modes of data communicationTafadzwa Gonera
This document discusses different modes of data communication, including wired and wireless technologies. It describes protocol models like OSI and TCP/IP that define network layers. Wired technologies covered include coaxial cable, fiber optic cable, and twisted pair cable. Wireless technologies discussed are Bluetooth, WiMAX, infrared, and Wi-Fi. The document provides definitions, diagrams, advantages and disadvantages of each technology discussed.
The document provides an introduction to computer networking concepts. It defines a network as consisting of two or more connected computers that can share resources and information. Networks allow for sharing of hardware, software, data, and centralized administration. There are different types of networks classified by transmission medium (wired vs wireless), size (LAN vs WAN), management method (peer-to-peer vs client/server), and topology (bus, star, ring). Common transmission media include twisted-pair cables, coaxial cables, and fiber-optic cables. LANs are small, local networks while WANs connect multiple LANs over longer distances using technologies like broadband. Client/server networks have dedicated server computers that provide resources to
Similar to 10-Ch17-WirelessLANsTech_IEEE802.11wireless.ppt (20)
Discover the benefits of outsourcing SEO to Indiadavidjhones387
"Discover the benefits of outsourcing SEO to India! From cost-effective services and expert professionals to round-the-clock work advantages, learn how your business can achieve digital success with Indian SEO solutions.
Securing BGP: Operational Strategies and Best Practices for Network Defenders...APNIC
Md. Zobair Khan,
Network Analyst and Technical Trainer at APNIC, presented 'Securing BGP: Operational Strategies and Best Practices for Network Defenders' at the Phoenix Summit held in Dhaka, Bangladesh from 23 to 24 May 2024.
Honeypots Unveiled: Proactive Defense Tactics for Cyber Security, Phoenix Sum...APNIC
Adli Wahid, Senior Internet Security Specialist at APNIC, delivered a presentation titled 'Honeypots Unveiled: Proactive Defense Tactics for Cyber Security' at the Phoenix Summit held in Dhaka, Bangladesh from 23 to 24 May 2024.
HijackLoader Evolution: Interactive Process HollowingDonato Onofri
CrowdStrike researchers have identified a HijackLoader (aka IDAT Loader) sample that employs sophisticated evasion techniques to enhance the complexity of the threat. HijackLoader, an increasingly popular tool among adversaries for deploying additional payloads and tooling, continues to evolve as its developers experiment and enhance its capabilities.
In their analysis of a recent HijackLoader sample, CrowdStrike researchers discovered new techniques designed to increase the defense evasion capabilities of the loader. The malware developer used a standard process hollowing technique coupled with an additional trigger that was activated by the parent process writing to a pipe. This new approach, called "Interactive Process Hollowing", has the potential to make defense evasion stealthier.
2. Overview
• Wireless LAN uses wireless transmission medium.
• Problems like high prices, low data rates, occupational safety
concerns, and licensing requirements have been addressed.
• Popularity of wireless LANs has grown rapidly.
Topics covered:
1. Wireless LAN applications
2. Wireless LAN requirements
3. Wireless LAN Technology
3. Four application areas for wireless LANs:
a. LAN extension
b. Cross-building interconnect
c. Nomadic access and
d. Ad hoc networks
1. Wireless LAN applications
4. 1. Wireless LAN applications -
a. LAN Extension
• Wireless LAN saves installation of LAN cabling, eases
relocation and other modifications to network structure
• But this motivation for wireless LANs was overtaken by
events like greater awareness of the need for LANs
• Also new buildings were designed to include extensive
prewiring for data applications.
• Second, with advances in data transmission technology, there
was an increasing reliance on twisted pair cabling for LANs
and, in particular, Category 3 and Category 5 UTP.
5. Reasons for increasing reliance on twisted pair cabling for LANs
are:
• Most older buildings already wired with Cat 3 cable
• Newer buildings are prewired with Cat 5
Thus, the use of a wireless LAN to replace wired LANs has not
happened to any great extent.
But in a number of environments, wireless LAN is an alternative to
a wired LAN.
Examples include
Buildings with large open areas
Manufacturing plants, stock exchange trading floors,
Warehouses
Historical buildings
Small offices where wired LANs are not economical
1. Wireless LAN applications -
a. LAN Extension
6. For example, a manufacturing facility typically has an office area
that is separate from the factory floor but that must be linked to it
for networking purposes.
Therefore, a wireless LAN will be linked into a wired LAN
on the same premises.
Thus, this application area is referred to as LAN extension.
1. Wireless LAN applications -
a. LAN Extension
8. Single Cell Wireless LAN Configuration(single CM)….
Includes
1. Backbone wired LAN
2. Control Module(CM) – interfaces to wireless LAN. Contains
• bridge or router to link wireless to wired
• polling or token passing scheme
• some of the end systems are standalone devices, such as a
workstation or a server.
• Hubs or other user modules (UMs) that control a number of
stations outside a wired LAN
9. Multi-Cell Wireless LAN Configuration(multiple CM
interconnected by wired LANS
each CM supports a number of wireless end systems within its range.
Application is in Infrared LANs txns. limited to single rooms. So one
CM in each room is required.
10. Wireless LAN applications
b. Cross-Building Interconnect
• Connect LANs in nearby buildings
• Point-to-point wireless link used b/w buildings
• Connect bridges or routers
• Not a LAN as such but usual to include this application
under heading of wireless LAN
11. Wireless LAN applications
c. Nomadic Access
• Provides wireless link between LAN hub and mobile data
terminal like
—Laptop or notepad computer &
—Enable employee returning from trip to transfer data from
portable computer to server
• Also useful in extended environment such as campus or
cluster of buildings
—Users move around with portable computers &
—May wish access to servers on wired LAN
13. Wireless LAN applications
d. Ad Hoc Networking
• Ad Hoc Network is a peer-to-peer network
• Set up temporarily to meet some immediate need
• E.g. group of employees, each with laptop or palmtop, in
business or classroom meeting
• employees link their computers in a Network for duration of
meeting
• there is no infrastructure for an ad hoc network. Rather, a peer
collection of stations within range of each other may
dynamically configure themselves into a temporary network.
Compare all three..
15. 2. Wireless LAN Requirements
Same as any LAN
— High capacity, short distances, full connectivity, broadcast capability
• Throughput: make efficient use of wireless medium for max. throughput
• Number of nodes: should support hundreds of nodes across multiple cells
• Connection to backbone LAN: Use control modules to connect to both
types of LANs (wired and wireless)
• Service area: 100 to 300 m
• Low power consumption:Need long battery life on mobile stations
— Mustn't require nodes to monitor access points or frequent handshakes
• Transmission robustness and security:Interference prone and easily
eavesdropped. So design properly.
• Collocated network operation:Two or more wireless LANs in same area
• License-free operation
• Handoff/roaming: Move from one cell to another
• Dynamic configuration: Addition, deletion, and relocation of end systems
without disruption to users
16. Technology
• Infrared (IR) LANs: Individual cell of IR LAN limited to
single room
—IR light does not penetrate opaque walls
• Spread spectrum LANs: Mostly operate in ISM (industrial,
scientific, and medical) frequency bands
—No Federal Communications Commission (FCC) licensing
is required in USA
• Narrowband microwave: Microwave frequencies but not use
spread spectrum
—Some require FCC licensing
17. Infrared LANs - Strengths and Weaknesses (advantages over
microwave radio LANs approaches.)
Infrared offers a number of significant advantages
over microwave radio approaches.
1. Unlimited Spectrum for infrared, so extremely
high data rates, but microwave radio spectrum is
limited.
2. Unregulated Spectrum (free, loose, free for all) for
infrared worldwide, but microwave radio spectrum
is regulated.
3. IR detect only amplitude of optical signals but
microwave Rxrs must detect frequency or phase.
18. Infrared LANs - Strengths and Weaknesses (advantages over
microwave radio approaches.)
3. Infrared shares some properties of visible light
Diffusely reflected by light-colored objects
• Use ceiling reflection to cover entire room
Does not penetrate walls or other opaque objects
• So more easily secured against eavesdropping than microwave
• And separate installation in every room without interference
4. Inexpensive and simple
Uses intensity modulation, so receivers need to detect only amplitude
Weakness : Background radiation from Sunlight & indoor lighting
• Radiation appears as Noise,
• So txr requires higher power and limiting range
• But txr power is limited by concerns of eye safety and power
consumption
19. Infrared LANs - Transmission Techniques
Three alternative transmission techniques for IR
data transmission:
1. the transmitted signal can be focused and aimed
(as in a remote TV control);
2. it can be radiated omnidirectionally; or
3. it can be reflected from a light-colored ceiling.
20. Infrared LANs - Transmission Techniques
• Directed-beam IR
—Point-to-point links
—Range depends on power and focusing
• Can be kilometers
• Used for building interconnect within line of sight
—Indoor use to set up token ring LAN
—IR transceivers positioned so that data circulate in ring
• Omnidirectional
—Single base station within line of sight of all other stations
• Typically, mounted on ceiling
—Acts as a multiport repeater
—Other transceivers use directional beam aimed at ceiling unit
• Diffused configuration
—Transmitters are focused and aimed at diffusely(to spread or
scatter widely or thinly) reflecting ceiling
21. Spread Spectrum LANs
Hub Topology
• Usually use multiple-cell arrangement
• Adjacent cells use different center frequencies
• Hub is typically mounted on ceiling
—Connected to wired LAN
—Connect to stations attached to wired LAN and in other cells
—May also control access
• IEEE 802.11 point coordination function
—May also act as multiport repeater
• Stations transmit to hub and receive from hub
—Stations may broadcast using an omnidirectional antenna
• Logical bus configuration
• Hub may do automatic handoff
— when signal weakening, hand off to another hub
22. Spread Spectrum LANs
Peer-to-Peer Topology
• No hub
• MAC algorithm such as CSMA used to control
access
• Preferred topology for Ad hoc LANs
23. Spread Spectrum LANs
Transmission Issues
• Licensing regulations differ from one country to another
• USA FCC authorized two unlicensed applications within the
ISM band:
—Spread spectrum - up to 1 watt
—Very low power systems- up to 0.5 watts
—902 - 928 MHz (915-MHz band)
—2.4 - 2.4835 GHz (2.4-GHz band)
—5.725 - 5.825 GHz (5.8-GHz band)
—2.4 GHz also in Europe and Japan
—Higher frequency means higher potential bandwidth
• Potential for Interference
—Devices at around 900 MHz, including cordless telephones, wireless
microphones, and amateur radio
—Fewer devices at 2.4 GHz; microwave oven
—Little competition at 5.8 GHz
• Higher frequency band, more expensive equipment
24. Narrow Band Microwave LANs
Using microwave radio frequency band with narrow bw.
• Just wide enough to accommodate signal
• Until recently, all products used licensed band
• At least one vendor has produced LAN product in ISM band
Licensed narrowband RF & UnLicensed narrowband RF
• ISM band(unlicensed bands) - Industrial, Scientific and
Medical Radio band. Ex equipment are Microwave ovens,
cordless phones, medical diathermy machines, military radars and
industrial heaters
25. Licensed Narrowband RF
• Microwave frequencies usable for voice, data, and video licensed within
specific geographic areas to avoid interference
—Radium 28 km
—Can contain five licenses
—Each covering two frequencies
—Motorola holds 600 licenses (1200 frequencies) in the 18-GHz range
—Cover all metropolitan areas with populations of 30,000 or more in
USA
• Use of cell configuration
• Adjacent cells use nonoverlapping frequency bands
• Motorola controls frequency band
—Can assure nearby independent LANs do not interfere
• All transmissions are encrypted
• Licensed narrowband LAN guarantees interference-free communication
• License holder has legal right to interference-free data channel
26. Unlicensed Narrowband RF
• 1995, RadioLAN introduced narrowband wireless LAN using
unlicensed ISM spectrum
—Used for narrowband transmission at low power
• 0.5 watts or less
—Operates at 10 Mbps
—5.8-GHz band
—50 m in semiopen office and 100 m in open office
• Peer-to-peer configuration
• Elects one node as dynamic master
—Based on location, interference, and signal strength
• Master can change automatically as conditions change
• Includes dynamic relay function
• Stations can act as repeater to move data between stations that
are out of range of each other
27. 14.27
14-1(F) IEEE 802.11 and 17.3 (S)
IEEE has defined the specifications for a wireless LAN,
called IEEE 802.11, which covers the physical and data
link layers.
Architecture n Services
MAC Sublayer
Physical Layer
Topics discussed in this section:
28. IEEE 802.11 – Architecture and Services
1. Architecture
• 802.11 architecture includes
Basic service set (BSS)
Extended service set (ESS)
30. IEEE 802.11 – Architecture and Services
BSS
covers the physical and data link layers.
• Smallest building block for wireless LAN is basic service set
(BSS)
—Contains Number of stations
—With Same MAC protocol
—Competing for access to same shared wireless medium
• BSS is made of stationary or mobile wireless stations and an
optional central base station, known as the access point (AP).
• BSS with an AP - connect to backbone distribution system (DS)
through access point (AP)
—AP functions as bridge
• MAC protocol may be distributed or controlled by central
coordination function in AP
• BSS generally corresponds to cell
• DS can be switch, wired network, or wireless network
32. BSS Configuration
• Simplest: each station belongs to single BSS
—Within range only of other stations within BSS
• Can have two BSSs overlap
—Station could participate in more than one BSS
• Association between station and BSS dynamic
—Stations may turn off, come within range, and go out of
range
33. Extended Service Set (ESS)
• Two or more BSS interconnected by DS (backbone
distribution system)
—Typically, DS is wired backbone but can be any network
• Appears as single logical LAN to LLC
34. Access Point (AP)
• Logic within station that provides access to DS
—Provides DS services in addition to acting as station
• To integrate IEEE 802.11 architecture with wired
LAN portal
• Portal logic implemented in device that is part of
wired LAN and attached to DS
—E.g. Bridge or router
36. Categorizing Services - 9
1. Station services implemented in every 802.11 station
Including AP stations
2. Distribution services provided between BSSs
May be implemented in AP or special-purpose device
• Three services used to control access and confidentiality
• Six services used to support delivery of MAC service data
units (MSDUs) between stations
37. Categorizing Services - 9
1. Distribution of messages within DS
Distribution
Integration
2. Association related services
3 types based on mobility(type of station)
No transition
BSS transition
ESS transition
3 types based on association with AP
Association – initial. b/w station n AP
Reassociation – established association to be transferred from one
AP to another. (so station can go from one BSS to another)
Disassociation – existing association terminated
39. Services
Service Provider Category
Association Distribution system MSDU delivery
Authentication Station LAN access and
security
Deauthentication Station LAN access and
security
Dissassociation Distribution system MSDU delivery
Distribution Distribution system MSDU delivery
Integration Distribution system MSDU delivery
MSDU delivery Station MSDU delivery
Privacy Station LAN access and
security
Reassocation Distribution system MSDU delivery
40. Medium Access Control (MAC)
Sublayer
MAC layer covers three functional areas
• Reliable data delivery
• Access control
• Security
—Beyond our scope
41. Medium Access Control Sublayer -
Reliable Data Delivery
• 802.11 physical and MAC layers subject to unreliability
• Noise, interference, and other propagation effects result in loss
of frames
• Even with error-correction codes, frames may not successfully
be received
• Can be dealt with at a higher layer, such as TCP
• 802.11 includes frame exchange protocol for reliable data
delivery
42. Medium Access Control Sublayer –
Distributed Coordination Function (DCF) Protocol
• DCF protocol uses CSMA as acess protocol.
• If station has frame to transmit, it listens to medium
• If medium idle, station may transmit
• Otherwise must wait until current transmission complete
• No collision detection
—Not practical on wireless network
—Dynamic range of signals very large
—Transmitting station cannot distinguish incoming weak signals from
noise and effects of own transmission
• DCF includes delays
• Interframe space
43. Medium Access Control Sublayer -
Interframe Space
• Single delay known as interframe space (IFS)
• Using IFS, rules for CSMA:
1. Station with frame senses medium
2. If busy station defers (delays) transmission
• Continue to monitor until current transmission is over
3. Once current transmission over, start another IFS
• If remains idle, back off random time and again sense
• If medium still idle, station may transmit
• During backoff time, if becomes busy, backoff timer is halted and
resumes when medium becomes idle
• To ensure stability, binary exponential backoff used
46. 14.46
For collision avoidance
When one station sends an RTS frame, other stations start
their NAV.
Then, before checking if channel is still busy or is now idle,
check if NAV has expired.
Network Allocation Vector (NAV)
48. Medium Access Control Sublayer -
Point Coordination Function (PCF)
• Alternative access method implemented on top of DCF
• Implemented only in infrastructure n/ws (not in AD Hocs)
• Used in time sensitive txns
• Has a centralized contention free polling access method
• AP performs polling of stations
• Uses PIFS (PCF IFS) when issuing polls
• Point coordinator polls in round-robin to stations configured
for polling
49. Medium Access Control Sublayer -
Priority
• Use three values for IFS
• SIFS (short IFS):
—Shortest IFS
—For all immediate response actions (see later)
• PIFS (point coordination function IFS):
—Midlength IFS
—Used by the centralized controller in PCF scheme when issuing polls
• DIFS (distributed coordination function IFS):
—Longest IFS
—Used as minimum delay for asynchronous frames contending for
access
51. Medium Access Control Sublayer -
MAC Frame Fields (1)
• Frame Control:
—Type of frame
—Control, management, or data
—Provides control information
• Includes whether frame is to or from DS, fragmentation information, and
privacy information
• Duration/Connection ID:
• Addresses:4
—Number and meaning of address fields depend on context
—Types include source, destination, transmitting station, and receiving
station
• Sequence Control
• Frame Body
• Frame Check Sequence
—32-bit cyclic redundancy check
52. Medium Access Control Sublayer -
Frame Types - 3
3 categories of frames:
1. Management frames
2. Control Frame
3. Data frames
53. 1. Management Frames
• Used to manage communications between stations
and Aps
• E.g. management of associations
—Requests, response, reassociation, dissociation, and
authentication
Medium Access Control Sublayer -
Frame Types cont…
54. 2. Control Frames
• Assist in reliable data delivery
• Power Save-Poll (PS-Poll)
• Request to Send (RTS)
• Clear to Send (CTS)
• Acknowledgment (ACK)
• Contention-Free (CF)-end
—Announces end of contention-free period
• CF-End + CF-Ack:
-- Acknowledges CF-end
—Ends contention-free period and releases stations from
associated restrictions
Medium Access Control Sublayer -
Frame Types cont…
56. 3. Data Frames – Data Carrying
• Data and control info
• Eight data frame subtypes
• First four carry upper-level data from source station to
destination station
• Data
• Data + CF-Ack
—Only sent during contention-free period
—Carries data and acknowledges previously received data
• Data + CF-Poll
• Data + CF-Ack + CF-Poll
Medium Access Control Sublayer -
Frame Types cont…
57. 3. Data Frames – Not Data Carrying
• Null Function
—Carries no data, polls, or acknowledgments
—Carries power management bit in frame control field to AP
—Indicates station is changing to low-power state
Medium Access Control Sublayer -
Frame Types cont…
61. 14.61
The CTS frame in CSMA/CA handshake can prevent collision
from
a hidden station.
Hidden station problem
Solution: use of handshake signals RTS & CTS
63. Required Reading
• Data and Computer Communications, William
Stallings, Chapter 17, 7th Edition.
• Data Communication and Networking, Behrouz A.
Forouzan, Chapter 14, 4th Edition.