Convenience: All notebook computers and many mobile phones today come equipped
with the WiFi technology required to connect directly to a wireless LAN.
Mobility: Employees can stay connected to the network even when they're not at their
desks. People in meetings can access documents and applications. Salespeople can check
the network for important details from any location.
Ease of setup: When you don't have to run physical cables through a location,
installation can be quick and cost-effective. Wireless LANs also make it easier to bring
network connectivity to hard-to-reach locations, such as a warehouse or factory floor.
Scalability: As your business operations grow, you may need to quickly expand your
network. Wireless networks can typically expand with existing equipment, while a wired
network might require additional wiring.
Security: Controlling and managing access to your wireless network is important to its
success. Advances in WiFi technology provide robust security protections so your data is
easily available to only the people you allow access.
Cost: It can cost less to operate a wireless LAN, which eliminates or reduces wiring costs
during office moves, reconfigurations, or expansions.
Wavelength: The physical distance from one point of the cycle to the same point in the
next cycle is called a wavelength , which is usually represented by the Greek symbol λ
Frequency : Number of times radio waves repeat their pattern per second. It is
measured in Hertz.
Reflection: When the radio wave hits the obstacle at a low angle, the wave (the entire
wave, or part of it) might bounce on the obstacle. This phenomenon is called reflection.
Multipath: A signal sent to a station travels in a straight line and reaches the
destination. A few microseconds later, copies of the same signal reflected on walls,
ceiling, and obstacles also reach the destination.
Refraction: Refraction occurs when a wave changes direction. This change in direction
usually happens when a wave passes from one medium to another (from air to water, for
Scattering: Reflection also occurs in the air itself, bouncing on dust or micro drops of
water (humidity). These multiple reflections are described as scattering .
Free Path Loss: Even without obstacles, a radio wave gets weaker as it moves away
from the emitting source because the energy of the wave spreads .
RSSI: Because the RF wave might have been affected by obstacles in its path, it is
important to determine how much signal is received by the other endpoint. The value
that indicates the amount of power received is called Received Signal Strength Indicator
IEEE : It defines how the signal is sent carrying data over unlicensed frequency band.
IEEE maintains and creates technical standards and protocols used by wireless LAN
Federal Communications Commission (FCC): In America and other countries in
America continents, FCC restrict the power and frequency can be used in that region.
ETSI (European Telecommunications Standards Institute): Controls Frequency
and power in Europe and other countries like Israel and some other countries.
Wi-Fi Alliance: It ensures that wireless products that are available to consumers
provide the features that the products claim to have.
Wireless personal-area networks (WPAN): Have a short range (up to 5–10 meters),
commonly use the 802.15 family of specifications to connect two or a few devices with low
power consumption. Bluetooth is an example of WPAN protocol.
Wireless local-area networks (WLAN): Consume more power but extend the connection
to about 300 feet (100 meters).
Wireless metropolitan-area network (WMAN): Extend the range to a larger geographic
area, such as a city or suburb. WMANs typically use licensed frequencies . Although
implementations in the ISM bands can also be found. WiMAX is an example of WMAN
Wireless wide-area network (WWAN): Provide connectivity over a wide geographical area.
Usually, WWANs are networks used for mobile phone and data service and are operated by
carriers. WWANs typically use licensed frequencies.
◦ Also known as Peer-to-Peer network.
◦ A first station defines the radio parameters and a connection name; the other stations
just need to detect the connection and adjust their own parameters to connect to the
first station and to each other.
◦ As soon as wireless devices connect to each other over a wireless network, a Basic
Service Set (BSS) is formed.
◦ The wireless network they form is called an Independent Basic Service Set (IBSS).
Infrastructure Mode: The AP functions as a translational bridge between 802.3 wired
media and 802.11 wireless media.
◦ BSS is the service provided by the AP.
Basic Service Area (BSA) :
Wireless Cell created by an AP – CISCO term.
Independent basic service set ( IBSSD):
Wireless network created by a Laptop.
Used in ADHOC Connection.
Basic service set – (BSS):
As soon as wireless devices (called “stations” in the 802.11 standard) connect to each
other over a wireless network a BSS is formed.
Distribution System (DS):
The wired section of the network that can be reached through the AP.
Extended service set – (ESS):
When the distribution system links two APs, or two cells, the group is called extended
Allows mobility roaming of wireless devices within a distributed system.
Service Set Identifier – (SSID):
Wireless Workgroup or Domain Name or simply a wireless network.
ASCI string providing a name to a wireless network.
Basic Service Set Identifier –(BSSID):
AP Radio MAC address associated with a SSID.
Multiple Basic Service Set Identifier –(MBSSID):
Having multiple SSIDs configured.
The first version of the 802.11 standard, released in 1997,
It described FHSS 1 Mbps, and DSSS 1 Mbps and 2 Mbps in the 2.4 GHz spectrum,
describing 14 channels.
802.11 is a rich family of protocols.
The standard was revised in 2007 to integrate all the amendments published over the
previous years (integrating 802.11a, b, d, e, g, h, i, and j). This cumulative version of
the standard is called 802.11-2007
802.11 was modified almost as soon as it was created to allow for faster speeds.
802.11b was published in 1999
It described CCK to bring the data rate to 5.5 Mbps and 11 Mbps.
802.11b was also too slow. A new amendment was published in 2003 introducing
OFDM to the 2.4 GHz band, and effectively. It allowing rates up to 54 Mbps.
802.11g is built to be backward compatible with 802.11b
When an 802.11b station is detected in the cell, the AP informs the cell in its
information broadcasts. These broadcasts contain 2 bits set to 1: “non-ERP (that is,
non-802.11g) present” and “use protection.
The downside of this protection mechanism is wasted time before each 802.11g
frame. This protection mechanism typically divides the overall throughput of the cell
The 802.11a amendment was published in 1999.
802.11a uses OFDM only (6 Mbps to 54 Mbps).
802.11a offers up to 23 nonoverlapping channels.
Channels are 20 MHz apart.
Primary 802.11n Components
40-MHz Channels Improved MAC
Two adjacent 20-MHz
combined to create a
MAC aggregation packs
smaller packets into a
Maximal Ratio Combining
802.11g and 802.11a use 20-
two carriers to increase the
MRC is used by the receiver with multiple antennas to optimally combine
energies from multiple receive chains. An algorithm eliminates out-of-
phase signal degradation.
The emitter can send the same signal from several antennas. By carefully
coordinating these signals based on the feedback transmitted by the 802.11n
receiving station, the emitter aims at making these signals be received in phase, thus
increasing the signal power level at the receiving station, allowing for longer range or
The emitter can send different simultaneous signals from different radios. The
802.11n receiver will receive these signals on all its radios. Each of the receive radios
independently decode the arriving signals. Then, each receive signal is combined
with the signals from the other radios. This results in additional throughput.
Extends the AP
Dual radio can
create dual half-
Overlap of 50%
A WGB provides wireless
connection from Ethernet port.
Several devices can benefit if
the WGB is connected to a hub
or a switch.
Extend the LAN by
Usually a few miles
Point to point or hub
Devices are connected with redundant connection between nodes; no
single point of failure
What is a Wireless Network?
A wireless local-area network (WLAN) uses radio waves to connect devices, such as
laptops, to the Internet and to your business network and applications
How Far Does the Signal Reach?
A wireless router or access point's signal typically extends up to approximately 300
Who Uses WLANs?
WLANs are frequently offered in public places such as cafes, hotels, and airport
lounges. In addition, many businesses have wireless networks throughout their
office buildings or campuses for employee and guest use.
What Equipment Do I Need?
Most laptops have built-in wireless networking. If yours doesn't, you'll need a
wireless network adapter card, which is typically inexpensive and easy to install.
Many routers act as WLAN access points. They connect multiple computers (and
wireless-capable printers) to a single WLAN and to the Internet.
You can extend WLANs throughout an area by placing additional wireless access
points in various locations. The access points extend the wireless signal's range and
How Can I Secure a WLAN?
There are many ways to secure your WLAN, including:
◦ Data encryption, which only gives authorized users access to information over
your wireless network
◦ User authentication, which identifies computers trying to access the network
◦ Secure access for visitors and guests
◦ Control systems, which protect the laptops and other devices that use the
Can two computers communicate using the wireless client cards without
an access point (AP)?
◦ Yes, two computers can communicate using the wireless client cards without an
AP. Connect the PC cards in Ad Hoc mode. This step eliminates peer interaction,
and one PC becomes the master.
Can you share the internet between two computers?
◦ No, you cannot share the internet. You need to install additional software to share
an internet connection.
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