3. Introduction
An alternative to Wired Technology , commonly used for
connecting devices in wireless mode.
Wi-Fi is a generic term that refers to the IEEE 802.11
communications standard for Wireless Local Area
Networks (WLANs).
Wi-Fi Network connect computers to each other, to the
internet and to the wired network.
Term Wi-Fi suggests Wireless Fidelity, resembling the
long-established audio-equipment classification term high
fidelity (in use since the 1930s ) or Hi-Fi (used since 1950),
it was never supposed to mean anything at all.
4. Wi-Fi Alliance
Wi-FiTechnology
Wi-Fi technology builds on IEEE 802.11 standards by IEEE
committee
IEEE 802.11 formed in 1990’s to develop a protocol &
transmission specifications for wireless LANs (WLANs)
The non-profit Wi-Fi Alliance formed in 1999 tests & certifies
equipment for compliance with them .
It consists of more than 300 companies from around the world.
Manufacturers whose products pass the certification process,
gain the right to mark those products with the Wi-Fi logo.
6. WiFi Architecture
Wi-FiTechnology
The purpose of Wi-Fi is
to hide complexity by
enabling wireless access to
applications and data,
media and streams.
It works on physical and
data link layer.
7. Wi-Fi channels
• 2.4 GHz band is 100 MHz wide & spans from 2.4 GHz to 2.5 GHz.
• There are 14 channels, each channel is 22 MHz wide and spaced 5
MHz
• 16.25 to 22 MHz of channel separation is required
• Adjacent channels overlap and will interfere with each other.
• Leaving three or four channels clear between used channels is
recommended to avoid interference.
• In 5 GHz bands
• extends from 5.180 to 5.825 GHz
• Twenty-five 20 MHz channels in the can be utilized when
designing a WLAN with a channel reuse pattern
• More channels , therefore less interference
9. Wi-Fi Standards
Wi-FiTechnology
802.11 number, followed by a letter or two for identifying standard and other
properties, such as the maximum speed and range of the particular device
802.11b
Most commonly adopted due to its lower cost
operated in the 2.4 GHz range & capable of transmitting at speeds of 11 Mbps
802.11a
Released in same year 1999,
operate at 5 GHz with transmissions speeds of 54 Mbps, its cost was high.
802.11g
Retained backwards compatibility to maintain support with existing hardware
and speed improvements
15
10. 802.11n
Introduced the first optional use of the 5GHz band, much less cluttered.
First use of MIMO antennas for higher parallel throughput.
Speeds can theoretically reach up to 450 Mbit/s, depending on the number of
antenna connections.
802.11ac
Last major revision to the main WiFi standard and Fastest WiFi version
First standard on the way to “Gigabit WiFi” where speeds can reach 1 Gbit/s,
Runs solely on the less cluttered 5 GHz band
Higher frequency and modulation rate allows for a higher speed, at the expense
of range
Wi-Fi Standards
15. Wi-Fi Security
WEP(Wired Equivalent Privacy) : The original encryption technique
specified by the IEEE 802.11 standard.
WPA(Wi-Fi Protected Access ): A new standard that provides improved
encryption security over WEP.
WPA2 : Improved version of WPA that uses Advanced Encryption Standard
(AES) technology.
Securing
Method
Encryption Type
Used
Security Level Notes
WEP
RC4 encryption
algorithm
Low
No longer used; it is can be
hacked easily
WPA TKIP Protocol High
provides improved
encryption security over
WEP
WPA2 CCMP Protocol Very High
An improved version of
WPA that uses Advanced
Encryption Standard
16. Advantages
Wi-FiTechnology
Freedom & Mobile Access – Allows to work from any location
getting signal.
Ease of Installation & Flexibility – Quick and easy to setup
Reliability & Speed
Setup Cost – No cabling required.
Scalable – Can be expanded with growth.
Security
17. Limitations
Wi-FiTechnology
Interference
Limited range
Speed – Slower than cable.
Range – Affected by various medium.
Reduced by walls, glass, water, etc.
Security – Greater exposure to risks.
Unauthorized access and Compromising data.
18. Focussing on Internet of Things (IoT)
Operate in the sub-1 GHz spectrum, providing long-range and low-power
operation
802.11ad
• Takes a different approach, aiming for a massive boost in speed at the expense of
range.
• Opts for a very high 60 GHz transmission frequency enabling data speeds to reach
around 7 Gbit/s.
• Major trade-off to range, as the frequency cannot penetrate walls
• requires a direct line of sight to the router & an expensive technology to implement
Future of WiFi
19. 802.11ah
• Reach up to 1 kilometre (3,300 ft), providing that certain conditions are met
• For greater coverage, transmitted at just 900 MHz
• Speeds decrease from the transmitter and devices will only be able to
transmit data at speeds between 150 Kbit/s and 18 Mbit/s
• Suited to low power devices for short bursts of data, such as IoT devices.
802.11af
• Also called White-Fi or Super WiFi
• Uses television spectrum frequencies between 54 MHz and 790 MHz, making
this the longest range WiFi technology yet, with miles of coverage
• Helpful for long distance IoT communication
• Acceptable speeds over these distances because of the lack of interference
Future WiFi Standards
Stallings Figure 17.3 illustrates the model developed by the 802.11 working group. The smallest building block of a wireless LAN is a basic service set (BSS), which consists of wireless stations executing the same MAC protocol and competing for access to the same shared wireless medium. A BSS may be isolated or it may connect to a backbone distribution system (DS) through an access point (AP). The AP functions as a bridge and a relay point. In a BSS, client stations do not communicate directly with one another. Rather the MAC frame is first sent from the originating station to the AP, and then from the AP to the destination station. Similarly, a MAC frame from a station in the BSS to a remote station is sent from the local station to the AP and then relayed by the AP over the DS on its way to the destination station. The BSS generally corresponds to what is referred to as a cell. The DS can be a switch, a wired network, or a wireless network. When all the stations in the BSS are mobile stations that communicate directly with one another, not using an AP, the BSS is called an independent BSS (IBSS). An IBSS is typically an ad hoc network. In an IBSS, the stations all communicate directly, and no AP is involved.
A simple configuration is shown in Figure 17.3, in which each station belongs to a single BSS; that is, each station is within wireless range only of other stations within the same BSS. It is also possible for two BSSs to overlap geographically, so that a single station could participate in more than one BSS. Further, the association between a station and a BSS is dynamic. Stations may turn off, come within range, and go out of range. An extended service set (ESS) consists of two or more basic service sets interconnected by a distribution system. The extended service set appears as a single logical LAN to the logical link control (LLC) level.
The operation of an IEEE 802.11i RSN can be broken down into five distinct phases of operation, as shown in Stallings Figure 17.5. One new component is the authentication server (AS). The five phase are:
• Discovery: An AP uses messages called Beacons and Probe Responses to advertise its IEEE 802.11i security policy. The STA uses these to identify an AP for a WLAN with which it wishes to communicate. The STA associates with the AP, which it uses to select the cipher suite and authentication mechanism when the Beacons and Probe Responses present a choice.
• Authentication: During this phase, the STA and AS prove their identities to each other. The AP blocks non-authentication traffic between the STA and AS until the authentication transaction is successful. The AP does not participate in the authentication transaction other than forwarding traffic between the STA and AS. • Key generation and distribution: The AP and the STA perform several operations that cause cryptographic keys to be generated and placed on the AP and the STA. Frames are exchanged between the AP and STA only
• Protected data transfer: Frames are exchanged between the STA and the end station through the AP. As denoted by the shading and the encryption module icon, secure data transfer occurs between the STA and the AP only; security is not provided end-to-end.
• Connection termination: The AP and STA exchange frames. During this phase, the secure connection is torn down and the connection is restored to the original state.
