On stability and sampling schemes for wireless sensor networks

We consider a wireless sensor network in which the
sensor nodes are sources of delay insensitive traffic that needs to
be transferred in a multi-hop fashion to a common processing
center. We consider two data sampling schemes: a) the sensor
nodes have a sampling process independent of the transmission
scheme, and b) the sensor nodes sample new data only when it
has a opportunity of transmitting the data. The first system is like
the packet radio network for which exact analysis is not available.
We also show that the stability condition proposed in the PRN
literature is not accurate. A correct stability condition for such
a system is provided. It is also observed that the second scheme
gives a better performance in terms of delays and moreover is
amenable to analysis.
We then address the problem of optimal routing that aims
at minimizing the end-to-end delays. Since we allow for traffic
splitting at source nodes, we propose an algorithm that seeks the
Wardrop equilibrium instead of a single least delay path. The
algorithm is implemented in TinyOS and numerical results from
the implementation are provided.