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1. Issues in Designing Adhoc Wireless routing Protocols T S
Pradeep kumar h"p://www.nsnam.com
2. Issues in routing Mobility Bandwidth constraint Error prone
shared broadcast radio channel hidden and exposed terminal problems
Resource Constraints
4. Bandwidth constraints Radio band is limited, hence the data
rates are smaller when compared with the wired network so bandwidth
has to be used carefully to avoid overheads topology changes incur
more control overhead in turn consumes more bandwidth
5. shared broadcast radio channel wireless links have time
varying characteristics the routing protocols interacts with the
MAC layer for nding the routes or alternate routes so collision of
data and control packets
6. Hidden terminal problem Assuming B is the intermediate node
between A and C. A and C are sending data to B. A is hidden to C
and C is hidden to A. But both are visible to B. Since A and C are
hidden terminals, the packets sent by both the nodes at the same
time causes collision at node B. This can be avoided by using
RTS-CTS messages and also using RTS- CTS- Data- ACK.
7. Exposed Terminal Problem Node arrangement is ABCD B is
sending to A and at the same time C wants to send to D, but it
cannot, because of inability of use of radio spectrum. when B->
A and C->D to happen simultaneously, then the transmitting
frequency of C to be different from the receiving frequency.
8. Resource Constraints Battery life processing power size and
weight constraints
9. Ideal characteristics of routing protocol Fully distributed
(it is more fault tolerant than centralized) adaptive to frequent
topology changes route computation and maintenance must involve
minimum number of nodes localized, loop free and free from stale
routes number of broadcasts to be limited to avoid packet
collisions must converge to optimal route in case of path break or
path failure
10. Ideal characteristics of routing protocol Scarce use of
battery, bandwidth, computing power, memory, etc. store information
locally within the nodes (to store only the stable local route,
rather than the remote unstable route) Should support some Quality
of service and also to support time sensitive trafc