[ns] Bandwidth of wireless channel

[Daniel Mahrenholz]

Vinod schrieb:
> Actually, my problem involves calculating the effective bandwidth of a 
> wireless node (more specifically in a MANET). I guess the bandwidth_ 
> variable of MAC or Phy layers dont give this value.
>
> I am using the default parameters given in the AODV implementation.
>
> To put it more clearly, suppose node 'S' wants to send a pkt to 'R'.
> This pkt can either be forwarded through 'A' or 'B' (A & B are one hop 
> neighbors of S) depending on the bandwidth. So, I am planning to 
> calculate the effective bandwidths of A and B and choose the node 
> based on it.
>
> Can you (or anyone) suggest a way for this. I would be thankful

If nodes A and B are direct neighbors of S it is most likely that A and 
B have to share the medium either because they are in direct 
communication range or through the physical carrier sense. If I 
understand you right, you  try to compute the bandwidth that one node 
(e.g. S) can use to transmit a packet. A node has to share the medium 
with all nodes within interference range. So if S wants to transmit a 
packet via nodes A, D, and F to R and A,D are within interference range 
of S then the available bandwidth of S will reduce three times by the 
bandwidth required to transmit the packet. This is because the packet 
utilizes the medium (from S's point of view) when S transmits it, and 
when A and D forward it. Beyond this point S will not be influenced by 
the further forwarding of the packet because it is out of interference 
range.

In your case you have to take all possible routes and calculate the 
changes in the channel utilization for every node along the route or at 
least within your own interference range to know what effect the route 
decision will have on your available end-to-end bandwidth.

Hope this clarifies more than it confuses,
Daniel.