Page 123 - DCAP311_DCAP607_WIRELESS_NETWORKS

Unit 7: Wireless LAN

7.5.2 Disadvantages of Wireless LAN Notes

The disadvantages of WLAN are listed below:

z z Wireless LANs use radio waves to communicate. Special care needs to be taken to encrypt
information. Also the signal is much worse, and more bandwidth needs to be spent on
error correction.

z z A typical IEEE 802.11 access point has a range of meters from where devices can connect.
To extend the range more access points are needed.

z z There are many reliability problems, especially those connected to interference from other
devices.
z z Wireless LANs are much slower than wired ones; this may not matter for most users
though, because the bottleneck in a home network is usually the speed of the ADSL line
(used to connect to the Internet)

7.6 Ad Hoc Wireless LAN Network

A wireless ad hoc network is a decentralized type of wireless network. The network is ad hoc
because it does not rely on a preexisting infrastructure, such as routers in wired networks or
access points in managed (infrastructure) wireless networks. Instead, each node participates in
routing by forwarding data for other nodes, so the determination of which nodes forward data is
made dynamically on the basis of network connectivity. In addition to the classic routing, ad hoc
networks can use flooding for forwarding the data.

An ad hoc network typically refers to any set of networks where all devices have equal status on
a network and are free to associate with any other ad hoc network device in link range. Ad hoc
network often refers to a mode of operation of IEEE 802.11 wireless networks.

It also refers to a network device’s ability to maintain link status information for any number
of devices in a 1-link (aka “hop”) range, and thus, this is most often a Layer 2 activity. Because
this is only a Layer 2 activity, ad hoc networks alone may not support a routeable IP network
environment without additional Layer 2 or Layer 3 capabilities.
The earliest wireless ad hoc networks were the “packet radio” networks (PRNETs) from the
1970s, sponsored by DARPA after the ALOHA net project.
The decentralized nature of wireless ad hoc networks makes them suitable for a variety of
applications where central nodes can’t be relied on and may improve the scalability of networks
compared to wireless managed networks, though theoretical and practical limits to the overall
capacity of such networks have been identified.

Minimal configuration and quick deployment make ad hoc networks suitable for emergency
situations like natural disasters or military conflicts.

Notes The presence of dynamic and adaptive routing protocols enables ad hoc networks
to be formed quickly.

Self-Assessment

Fill in the blanks:
1. A .............................. is a device that allows wireless devices to connect to a wired network
using Wi-Fi, or related standards.

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