The many-to-one communication paradigm has an impact
on several design choices. For example, the authors in [27] note that in the
context of a many-to-one communication paradigm, network connectivity is a
function of the routing algorithm being used. This is because, when packets
9 Chapter 1 Design of Large-scale Sensor Networks
Aravind Iyer et al.
are to be routed towards the sink, the next hop neighbors of a node that are
located in the direction away from the sink do not contribute towards the
connectivity of the node.
3.4 Nodes with Limited Capabilities
Another important di?®erence between a cellular network or a wireless LAN,
and a sensor network is the device hardware. A wireless laptop, PDA or a
cell phone are relatively advanced devices as compared to a sensor node. The
latter is often restricted by a battery which is limited in energy and usually
cannot be replenished (typically a small lithium battery rated at a few hundred
mAh), slower computing speeds (about 4MHz), small memory (about
8KB flash memory and 512 bytes of RAM), low data rates (up to 20 Kbps)
and limited communication range (10-100 feet) (see [24] and the references
therein). These limitations have a direct impact on the functioning of the network
as a whole, and the protocols at di?®erent layers have to be designed by
taking into account these limitations.
3.5 Clustering for Scalability
Since sensor networks consist of a large number of nodes, it is clear that we
need distributed protocols for gathering data, and arbitrating the access to
the wireless channel, and these protocols should scale well as the number of
nodes in the network increases.
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