30-01-2013, 01:56 PM
Ad-Hoc Networks
Ad-Hoc Networks.ppt (Size: 2.96 MB / Downloads: 35)
Introduction (1):
Multi-hop Wireless Networks (MHWNs):
It is defined as a collection of nodes that communicate with each other wirelessly by using radio signals with a shared common channel.
There are several names for MHWNs; it could be called packet radio network, Ad-Hoc network or mobile network.
The nodes here could be named stations or radio transmitters and receivers.
Ad-Hoc Networks:
It is a type of MHWNs.
Nodes in the network are mobile in general.
The wireless hosts in such networks, communicate with each other without the existing of a fixed infrastructure and without a central control.
A mobile ad-hoc network can be connected to other fixed networks or to the Internet.
Most of the Ad-Hoc networks use the allocated frequencies for the Industrial, Scientific and Medical (ISM) band.
Advantages and Applications (1):
Ad-hoc networks have several advantages over the traditional networks, like:
Ad-hoc networks can have more flexibility.
It is better in mobility.
It can be turn up and turn down in a very short time.
It can be more economical.
It considered a robust network because of its non-hierarchical distributed control and management mechanisms.
Technical Challenges and Issues (1):
There are several challenges that Ad-Hoc network faces such as:
Limited wireless range.
Hidden terminals.
Packet losses.
Routes changes.
Devices heterogeneity.
Battery power constraints.
Ad-Hoc Wireless Media Access Protocols (1):
Why do we need for a media access protocol?
The medium is shared by all of the nodes.
If we give the node the freedom to send at any time, then that could result in a contention.
We can't have a central controller to manage the transmission process, because every node can move at any time.
Therefore, we will choose from the medium access control (MAC) protocols in order to use the shred medium in the most efficient way.