Wireless LAN Basics IEE802.11
Wireless LAN Basics IEE802.11
IEEE802.11
Overview
The fundamental building block of the 802.11 architec is the cell, known as the basic service set (BSS) in 802.11 parlance. A BSS typically contains one or more wireless stations and a central base station, known as an access point (AP) in 802.11terminology.
This is on IEEE 802.11 WiFi training is designed for people who work on development, testing and verification of IEEE 802.11 protocol. Students/Developer will learn the internals of IEEE 802.11 protocol that helps them with a much better understanding of their current IEEE 802.11 work.
The fundamental building block of the 802.11 architec is the cell, known as the basic service set (BSS) in 802.11 parlance. A BSS typically contains one or more wireless stations and a central base station, known as an access point (AP) in 802.11terminology.
This is on IEEE 802.11 WiFi training is designed for people who work on development, testing and verification of IEEE 802.11 protocol. Students/Developer will learn the internals of IEEE 802.11 protocol that helps them with a much better understanding of their current IEEE 802.11 work.
OSI LAYERS:
The Open Systems Interconnection model (OSI model) is a conceptual model that
characterizes and standardizes the communication functions of a
telecommunication or computing system without regard to their underlying
internal structure and technology.
Upper layers:
Upper layers:
- 7.
application
- 6.
presentation
- 5.
session
Lower layers:
- 4.
transport
- 3.
network
- 2.
data link
- 1.
physical
What is the difference between WLAN and WiMAX?
Answer-1.WLAN is used
as wireless local area network for providing connectivity between WLAN compliant
devices. WiMAX is used as wide area network for providing access between
various wireless devices. WLAN standards are evolving including 11a, 11b, 11g,
11n, 11ac, 11ad and more. WiMAX follows IEEE standards viz. 16d and 16e
WLAN Network
Basics
WLAN network topology
– Infrastructure Mode
– Repeater Mode
– Bridge Mode
– Ad-hoc Mode
Channel scanning and synchronization
– Passive Scan
– Active Scan
Authentication and association
– Open Authentication
– Shared Key Authentication
WLAN network topology
– Infrastructure Mode
– Repeater Mode
– Bridge Mode
– Ad-hoc Mode
Channel scanning and synchronization
– Passive Scan
– Active Scan
Authentication and association
– Open Authentication
– Shared Key Authentication
Explain the WLAN physical layer frame as
per 802.11a?
WLAN has physical layer frame formats different in 11a, 11b, 11g, 11n
and 11ac? They all have
three generic fields i.e. preamble, header and data payload (PSDU). Preamble
carries STF (short training field) and LTF (long training field) used for front
end synchronization. Front end synchronization includes time offset estimation
and correction; frequency offset estimation and correction and channel
estimation and equalization. Header carries two important parameters rate and
length. Rate specify modulation-code rate of the data payload part and length
field specify length of data payload in units of OFDM symbol
What is the difference between 802.11a, 11b,
11g and 802.11n? Answer-3.The difference between the 11a, 11b, 11g and 11n
lies in terms of data rate, frequency of operation, distance coverage and more
Physical Layer
Technologies
Radio channels and frequencies
– Frequency Channel Allocation for 802.11a/b/g
Modulation technologies
– Direct Sequence Spread Spectrum
– Orthogonal Frequency Division Multiplexing (OFDM)
PHY data rates used
– 802.11b
– 802 11a
– 802 11g
– 802 11n
Improving data transfer:diversity and polarization
– Antenna Diversity
– Polarization
Radio channels and frequencies
– Frequency Channel Allocation for 802.11a/b/g
Modulation technologies
– Direct Sequence Spread Spectrum
– Orthogonal Frequency Division Multiplexing (OFDM)
PHY data rates used
– 802.11b
– 802 11a
– 802 11g
– 802 11n
Improving data transfer:diversity and polarization
– Antenna Diversity
– Polarization
What are the messages exchange between
STA and AP in WLAN?
There are various messages exchanged between
Station (STA) and Access Point (AP) in a WLAN network for various purpose such
as establishing connection, data transfer, terminate the connection and more.
Access points are devices which help extend wired network with wireless
capabilities
What is the change in WLAN-11ac with
respect to previous versions of WLAN
WLAN-11ac has been introduced after
previous version of WLAN which include 802.11a, 11b, 11g and 11n. 80MHz channel
bandwidth is added
Wireless LAN
Standards
802.11a – 54 Mbps standard, 5 GHz signaling (ratified 1999)
802.11b – 11 Mbps standard, 2.4 GHz signaling (1999) 11 Mbps standard, 2.4 GHz signaling (1999)
802.11c – operation of bridge connections (moved to 802.1)
802.11d – worldwide compliance with regulations for use of wireless signal
spectrum (2001)
802 11e – Quality of Service (QoS) support (2005)
802.11f – Inter access point protocol to support roaming clients (2003)
802.11g – 54 Mbps standard, 2.4 GHz signaling (2003)
802.11h – Enhanced version of 802.11a to support European regulatory
requirements (2003)
802.11i – Security improvements for the 802.11 family (2004)
802.11j – Enhancements to 5 GHz signaling to support Japan regulatory
requirements (2004) requirements (2004)
802.11k – WLAN system management (in progress)
802.11l – Skipped to avoid confusion with 802.11i
802.11a – 54 Mbps standard, 5 GHz signaling (ratified 1999)
802.11b – 11 Mbps standard, 2.4 GHz signaling (1999) 11 Mbps standard, 2.4 GHz signaling (1999)
802.11c – operation of bridge connections (moved to 802.1)
802.11d – worldwide compliance with regulations for use of wireless signal
spectrum (2001)
802 11e – Quality of Service (QoS) support (2005)
802.11f – Inter access point protocol to support roaming clients (2003)
802.11g – 54 Mbps standard, 2.4 GHz signaling (2003)
802.11h – Enhanced version of 802.11a to support European regulatory
requirements (2003)
802.11i – Security improvements for the 802.11 family (2004)
802.11j – Enhancements to 5 GHz signaling to support Japan regulatory
requirements (2004) requirements (2004)
802.11k – WLAN system management (in progress)
802.11l – Skipped to avoid confusion with 802.11i
What is the difference between WiFi and
Bluetooth?
WiFi fall under WLAN category while
Bluetooth fall under WPAN category. WLAN specifications are published under
IEEE 802.11 and Bluetooth under IEEE 802.15 standards. Bluetooth is the
standard for wireless personal area networks or WPAN. It allows high speed
transmission of data over very short distances.
802.11m – Maintenance of 802.11 family documentation
802.11n – Future 100+ Mbps standard (in progress)
802.11m – Maintenance of 802.11 family documentation
802.11n – Future 100+ Mbps standard (in progress)
Protocol
Architecture
The Physical Medium Dependent Layer
The Data Link Layer
The Network Layer
The Transport Layer
The Physical Medium Dependent Layer
The Data Link Layer
The Network Layer
The Transport Layer
Explain OSI stack and differentiate with
TCPIP protocol stack?
OSI protocol stack is the generic stack
developed to make it easy for different manufacturers devices inter-operate
without any interfacing issues. TCP IP stack is specifically designed for
internet applications.
802.11 MAC
Protocol
Framing data to be transmitted
– Management Frames
– Control Frames
– Data Frames
Spacing between frames
– Inter Frame Spaces (IFS)
Avoiding collisions: carrier sensing
– Physical Carrier Sensing
– Virtual Carrier Sensing
Framing data to be transmitted
– Management Frames
– Control Frames
– Data Frames
Spacing between frames
– Inter Frame Spaces (IFS)
Avoiding collisions: carrier sensing
– Physical Carrier Sensing
– Virtual Carrier Sensing
What is the difference between ad-hoc
and infrastructure mode in IEEE 802.11? \
In ad-hoc mode WLAN mobile and stationary
terminals referred as STAs (stations) communicate directly. In the
infrastructure mode STAs communicate via entity called as AP (Access Point). It
is similar to mesh and star topologies used in other wireless networks.
Infrastructure mode used to connect with wired network.
Security
Protocols in WLANs
Common WLAN Attacks
– Passive Attacks: eavesdropping
– PHY Layer attacks: RF Jamming
– Active Attacks: hacking
– Man in the Middle Attack
WLAN Security Solutions
– WEP-SharedKey
– WPA-PSK
– WPA-Open
– Server Based Authentication
– Server-based security: 802.1x / 802.11i
Common WLAN Attacks
– Passive Attacks: eavesdropping
– PHY Layer attacks: RF Jamming
– Active Attacks: hacking
– Man in the Middle Attack
WLAN Security Solutions
– WEP-SharedKey
– WPA-PSK
– WPA-Open
– Server Based Authentication
– Server-based security: 802.1x / 802.11i
About the Author
1 comments
This is a great blog, you can read my article BROTHER PRINTER TO WIFI
ReplyDelete