Getting Node Position, Neighbors, Distances and Transmission Power etc., Under ns-2

What is the best way you think to update the node position and number of neighbours? I need an effective way from your experience and knowledge.

The hello mechanism is the only effective way to get update about a node’s current position(if we are not considering a centralized location service).
Particularly, in AODV, there is an existing hello mechanism – you just need to activate it.

What is the best way to estimate the number of neighbours in the range to use enough power and also to reach them? I need an effective way from your experience and knowledge.

Just by receiving the hello replies from the neighbors is the only effective way to estimate the number of neighbors.
Again, in AODV, there is an existing hello mechanism – so that it will not increase the overhead while implementing neighbor discovery.
Over hearing the transmissions of neighbors at application layer is also the another way to count neighbors – but for that you may need to bring a node to promiscuous mode which will increase the overhead in all layers. I mean, you need to process all the packet at mac layer and send that information to Application layer.

What is the best way to calculate how many neighbours each node has? How can you calculate the optimum number of neigbors? I need an effective way from your experience and knowledge.

As far as MANET is concerned, there is no reliable way to calculate how many neighbors a node has – but over hearing the transmissions of neighbors is the another way to count neighbors.

What is the best way to estimate the distance and calculate that between nodes? I need an effective way from your experience and knowledge.

If you really know the absolute location of  two nodes, then the simple Euclidean distance calculation is enough. But there is no reliable way to calculate the absolute location of a node at any instant under a mobile condition.

What is the best way to adjust the transmission power? How can you select the optimum transmission power? I need an effective way from your experience and knowledge.

Changing TxPower in wireless Physical is the simplest way to change transmission power.
There is no reliable way for deciding  “optimum transmission power” – it will depend upon several factors – even those several factors also dynamically change in a highly mobile, high density network.
(that is why most of the dynamic tx power based AODV algorithms that you see in published paper will not really give any improved result in you try to implement it)

The only thing I know for reducing overall energy consumption is – reducing overhead in route request and reply mechanisms and  using more reliable paths to avoid link failures. Because, routing overhead is just using energy – link failures also initiate re-route discovery – so that consume energy again and again just for route discovery
(Here I am not mentioning the power used for transmitting actual data payload).

There are some funny algorithms you may see in the some published works based on reducing tx power with respect to local node density – trust me – they will not really work as it seems – Because, just decreasing the tx power with respect to the neighbor count will again reduce the neighbor count in the very next instant – so, it will just cause link failures at the very next instant of time and re-initiate route discovery and will increase the routing overhead and message overhead  and all kinds of other overhead to a very higher level.

So the following is my simple idea related with any genuine modified AODV implementation- I hope this may work

1. Keep tx power constant (a fixed value) for all  hello requests and replies- and  all route request and reply messages.
2. control the forwarding of  route request and reply messages based on the neighbor count at that node – this will help to establish more stable /reliable paths (and will reduce little bit of energy).
2. While routing a data packet through a neighbor, just change the transmission power to a minimum level to reach only up to that node (I mean, a assumed good, minimum distant) – after transmission of data packets, change the tx pwer to the original fixed value (for transmitting other kinds of packets)  so that normal working of routing will not get disturbed by any reduction in tx power. (this will also reduce little bit of over all energy consumption of the network).

Charles Pandian.