Page 134 - DCAP207_NETWORKS_DCAP406_COMPUTER_NETWORKS

Unit 8: Data Link Protocols

The common devices that are used in wireless networks are: Notes
Wireless Network Adaptor: A wireless network adapter is used to interface a computer to a
network. The wireless adaptors are available as hardware devices like PCI Ethernet cards,
PCMCIA devices, USB devices, etc. Some wireless network adapter devices for laptop computers
are integrated circuit chips pre-installed inside the computer. A software device called device
driver is used to communicate the network devices with the application software in different
operating system environments. Virtual adaptors as simply software program are widely used
in virtual private network (VPN).
Wireless Routers: The wireless routers are used to configure computers with wireless network
adapters. They may also possess a network switch to enable some computers to be connected
with Ethernet cables and share cable modem and DSL Internet connections. Some of the wireless
routers also have built in firewalls to protect the network from intruders. They are available
based on the wireless network protocols they support. The network protocols are 802.11g,
802.11a, 802.11b or a combination.
Wireless Access Points: They are configured nodes on wireless local area networks (WLANs) to
act as a central transmitter and receiver of WLAN radio signals and to support WiFi wireless
communication standards. The wireless access points (WAP) that are used in home or small
business networks are generally small, dedicated hardware devices possessing features of a
built-in network adapter, antenna and radio transmitter. However, small WLANs can function
without access points. They find use in ad hoc or peer-to-peer mode, access points support
infrastructure mode. The ad hoc infrastructures is used to bridge a WLAN with a wired Ethernet
LAN so that it may be scaled up to support more hosts.

Wireless Range Extender: A wireless range extender is deployed to increases the distance over
which a WLAN signal can spread. It thus improves the potential of signal to overcome obstacles
and enhances overall wireless network signal quality. The wireless range expander is also
known as range expanders or signal boosters and performs as a relay or network repeater by
picking up and reflecting WiFi signals from a network’s base router or access point.

Wireless Fidelity (WiFi)

WLAN are popularly known as the WiFi and operates on a family of 802.11 standards defined by
IEEE. The 802.11b is considered the first standard in 802.11 to enjoy widespread popularity.
However, the standards like 802.11a, 802.11b, 802.11g and 802.11n are available for WiFi. The
WiFi Alliance examines the specifications of 802.11 products and certifies them to ensure
compatibility with other products.
802.11: Refers to the generic name of a family of standards for wireless networking from the
IEEE. They define rules for communication on wireless local area networks (WLANs) in terms of
standards including 802.11a, 802.11b and 802.11g. The 802.11 that was developed around 1997,
define WLANs to operate at 1-2 Mbps. It is not in use today.

802.11a: It is a WLAN communication standard that supports a maximum bandwidth of 54 Mbps
with a radio signals in the frequency range above 5 GHz and provides improved performance
and reduced interference over 802.11b standard but at the cost of significantly enhanced cost of
access points and adapters. The 5 GHz frequency band of 802.11a limits the access point transmitter
to send signal over a one fourth area of 802.11b access point transmitter. The frequency spectrum
of 802.11a is regulated and dedicated to 802.11a devices only. Due to high frequency, walls and
other obstructions also significantly reduced the performance of 802.11a wireless networks
comparable 802.11b networks.
802.11b: It utilizes frequencies in the unregulated 2.4 GHz ranges, which may be allocated to
other radio devices and therefore encounters much more radio interference from them. However,

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