Image Processing Reference
In-Depth Information
multichannel approach is an interesting solution to increase the available bandwidth and decrease
contention, so further research might investigate the effect of the interferences as well as the obtain-
able network capacity. MAC protocols might exploit the benefits of multichannel approaches to
obtain bounded delay and good scalability at the same time. Another promising research trend for
MAC protocols might be the combination of spatial-correlation awareness with classical energy-
efficient techniques to improve the network lifetime even further.
In WSNs, the Application, Transport, Routing, MAC, and Physical layers have common require-
ments and are highly dependent on each other. As a result, cross-layering, where layers are integrated
with each other, is advisable. In addition, as layering of protocols introduces overheads for each layer,
even in terms of energy consumption, the integration of the protocol layers is an issue which deserves
further investigation.
An interesting research thread is represented by MAC protocols for the so-called WSANs. WSANs
may be considered a variation of WSNs [Aky], in which the devices deployed in the environment
act not only as sensors able to sense environmental data, but also as actors
∗
able to react and to affect
the environment.
WSANs have some notable differences from WSNs. First, actors are usually resource-rich devices
equipped with better processing capabilities, stronger transmission power, and a longer battery life
than typical sensor nodes. Second, in WSANs, depending on the application, real-time computation
and communication are very important issues, since timely actions have to be performed in the envi-
ronment after sensing occurs. hird, the number of sensor nodes in WSANs may be in the order of
hundreds or thousands, but the number of actors is much lower than the number of sensors. Finally,
in order to provide effective sensing and acting, a distributed local coordination mechanism is nec-
essary among sensors and actors. hese differences make the existing MAC protocols developed for
ad-hoc networks or WSNs not suitable for WSANs.
Another promising field of research is physical computing systems. hese systems derive from the
confluence of embedded and real-time systems with wireless, sensor, and networking technologies
through the seamless integration of computing and physical world via sensors and actuators [Sta].
This confluence is leading to the deployment of networks for the collaborative processing of physical
information. Physical computing systems are typically very large and dense and require real-time
operation, dependability, security, safety, efficiency, and adaptivity. As current WSNs protocols do
not provide all these features, further research is needed to address the challenges raised by this kind
of systems.
References
[Aky]
I. F. Akyildiz and I. H. Kasimoglu, Wireless sensor and actor networks: Research challenges,
Ad Hoc Networks
, (), -.
[Che]
X. Chen, P. Han, Q. He, S. Tu, and Z. Chen, A multi-channel MAC protocol for wireless sen-
sor networks, in
Proc. of the th IEEE International Conference on Computer and Information
Technology, CIT
,Washington,DC,p.,Sept.
[Chi]
O.Chipara,Z.He,Q.Chen,G.Xing,X.Wang,C.Lu,J.Stankovic,andT.Abdelzaher,Real-time
power-aware routing in sensor networks, in
Proc. of IWQoS , the th IEEE International
Workshop on Quality of Service
, pp. -, New Haven, CT, Jun .
∗
∗The concept of actor is different from the concept of actuator. An actuator is a device that converts an electrical control
signal to a physical action. An actor not only is able to act on the environment by means of one or several actuators, but is
also a network entity that receives, transmits, processes, and relays data.
