Sunday, April 09, 2006

Providing Push or Pull in MANET

Asymmetry happens in MANET not only due to communication behavior, but also due to

  • Ratio of clients and servers

  • Difference in downlink bandwidth and uplink ones

  • Data Volume

  • Hot data items

Push has a obvious advantage in MANET, as it

  • takes same bandwidth for any subscribers

  • Conserves energy by eliminating energy consuming uplink transmission, yields only if needy items are pushed

  • Backchannel is missing or having poor bandwidth

Pull is also needed in MANET, as it

  • is required for custom query or in on-demand mode

  • much prefered mode when authorization is required.

A very interesting fact in regard to hot data items data dissemination is,
If p1,p2....,pn are the popularity ratios of data item, then their broadcast frequencies are f1,f2,...,fn, where fk = sqrt(pk)/sum of (sqrt(pks)) (By a paper of Imielinski et al)

Obviously, it is very favoring result for the push mode if we can sort hot data items at the cost of average access latencies of data items.

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