Due Oct 19, 2007, in class.
You are encouraged to consult literature and borrow ideas. However, be certain to cite papers on which your answers are based. However, the homework must be individual effort.
Assume the log-distance path loss model with path loss exponent a = 2. Assume that if the distance between the sender and receiver is r, then any interferer is at a distance at least (1+D)r from the receiver. Assume that there are k interferers. If the SINR must be at least 5dB for an acceptable error rate, develop a bound for D in terms of k. Ignore noise. Assume that all transmitters transmit with the same power.
Study the AODV routing protocol in detail. Why is it that a routing table entry that is invalidated is not immediately deleted from the routing table? Explain clearly, preferably with an illustrating example, showing why this may create any problem.
What scenarios do you expect the proactive routing protocols to perform better than the reactive routing protocols? Where will the opposite be true?
Assume that some links in an ad hoc network is unidirectional. This happens when due to asymmetries in transceiver designs, transmit powers and/or radio propagation environments, a node A can hear another node B, but B cannot hear A. Apparently, this situation is prevalent in wireless communication systems. This creates subtle problems in routing protocols. For example, in the AODV protocol a route request can be propagated along a path which contains one or more of such unidirectional links. Thus, route replies cannot be received along this path. Suggest methods of tackling this problem either by arguing that this is not a problem, or by devising methods of ignoring unidirectional links or using them creatively in the routing protocol. (You can use AODV as the base routing protocol for your answer.)
Show that greedy geographic forwarding (distance based) cannot always route packets via the shortest path (in number of hops). It is sufficient to show an example.
Show that if links are unidirectional the planarization procedure described in the notes for RNG or GG (pick any one) would fail.