Page 132 - DCAP406_DCAP_207_Computer Networks

Unit 8: Data Link Protocols

Notes
Figure 8.11: LAN Extension using Fiber Modem and Cable

Fiber Fiber
Modem Modem
Optical
fiber

AUI
connection

Self Assessment

State whether the following statements are true or false:
8. Preamble is ending of the frame and used to establish bit synchronization with the help of
an alternating pattern of ones and zeros that is used by the receiver.
9. Ethernet was first designed and installed by Xerox Corporation.
10. Performance of Aloha or Slotted Aloha is determined with the help of throughput and
average delay.
11. Five classes of LCP frames exist.

8.8 Wireless LAN

Wireless networks provide connectivity by using radio signal frequency to communicate among
computers and other network devices and connection to the Internet anywhere in home or
office. The wireless networks are known as WiFi network or WLAN. Wireless LAN (WLAN)
enables hosts to communicate over short distances with the help of radio or infrared signal in
place of traditional network cabling. A WLAN helps in extending an existing wired LAN like
Ethernet by implementing access point to the edge of the wired network. The hosts connect to
the Internet through access point using a wireless network adapter like Ethernet adapter. The
wireless LAN adaptors also referred to as wireless NICs or wireless network cards are used in
each device that wishes to connect on a wireless network. Generally, the wireless networks are
built on wireless routers that act as base stations to provide a communication path through them
and enabling nearby computers to connect to the Internet or to each other. Wireless routers
perform like routers for wired networks. However, most wireless networks use a wireless
router. To reduce the cost of the wireless networks, the wireless networks may be built without
using routers. It is observed that no wireless hardware other than adapters is required to build
a small wireless LAN (WLAN). However, wireless access points and/or wireless routers are
used to increase the performance of a WLAN, accommodate more computers and increase the
network’s range. Access points that are provided as edge devices in wireless networks are
alternative to routers and help in extending a wireless networks by joining it to an existing
wired network. A single access point or router is considered to have sufficient range to span
most homes but office buildings require multiple access points. Along with the routers or access
points a wireless antenna is used to significantly increase the communication range of the
wireless radio signal. The wireless network with wireless adapter encodes the binary data to
radio frequency and wireless router transmits it. The reverse process takes place at the host
computer. The wireless network set is comprised of a computer fitted with a low power radio

LOVELY PROFESSIONAL UNIVERSITY 125