Paper #:[5.2 Mobile]: 16
Title:  Effects of power conservation, wireless coverage and
cooperation on data dissemination among mobile devices by Maria
Papadopouli and Henning Schulzrinne

PROBLEM

It is not always possible for users to have continuous access to the
Internet.  For example, users are currently unable to have cheap
continuous Internet throughout a metro area.  In addition, fixed
information servers, which are also known as "infostations", are
unlikely to be able to keep pace with the growing number of mobile
devices.  Consequently, a way is needed to increase data available to
users with only intermittent connectivity to the Internet while at the
same time tending to the needs of devices with limited power resources,
such as handheld devices.

NEW IDEAS AND STRENGTHS

*The authors created the 7DS system which may be used to disseminate
data while at the same time catering to the needs of handheld devices
that need power conservation methods.  This system, which utilizes
peer-to-peer dissemination out performs server-client  systems that do
not have mobile devices collaborate.
*Unlike other peer-to-peer systems, 7DS doesn't need to know its'
neighbors because it multicasts queries to groups.
*7DS has a query list of URLs that the system predicts the user will
visit.  Consequently, this will lessen the wait time for users to
access data if the predictions are accurate.
*Amount of work done in the network depends on resource availability,
such as battery power.  In addition, 7DS allows users to change the
power saving settings.   This is useful because the effectiveness of
the peer-to-peer is increased without power conservation.
*One strength of the paper is that it gave extensive scenarios that
ranged from popular data, which is on many user's devices, to typical
data, which is only on a few user's devices.


WEAKNESSES AND EXTENSIONS

*One weakness is that the authors only considered single-hop multicast.
I would have liked to have seen a comparison of single and multiple-hop
implementations or at least a guess on how they would expect a
multiple-hop implementation to fare.
*A possible extension to this paper is to resolve the differences among
multiple copies of a data object because several objects may match a
specific query.
*The paper mentions that forwarding does not improve performance.
However, I question this statement if the data is extremely rare and
not very many devices belong to the group that would hold the rare
data.