First,
the system is limited by the energy capacity of WSNs. Sensors are powered
by batteries and it may not be possible to recharge or replace them in many
applications. The system operations must be energy e?±cient. Second, the
system is limited by the bandwidth capacity of sensor nodes. The interactions
(i.e., communications) among the sensors must be kept minimal. Third, sensor
nodes do not have global topology information and they, sometimes, even
do not have global identifiers. Each sensor node only knows its own and its
neighbors??™ positions, and its operations must be based on its local information.
There are three important problems in such a distributed WSN, namely
location service, information dissemination and object tracking.
A. Location Service
Location service is a general obstacle for distributed networks. Without a
central node of control, updated location information about nodes should be
timely obtained before data can be exchanged among nodes correctly. However,
due to the limitation of their power and hardware capability, sensors will
be exhausted if they maintain tables for the location of all the others. Moreover,
if mobility is available, sensors are even harder to trace than other nodes.
Thus, location both in time and space has been identified as a key technology
for the successful deployment and operation of context-aware sensor network
services.
B. Information Dissemination
The main goal for WSNs is to provide distributed information services on
sensed data e?±ciently.
Pages:
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387