X.-C. Hao et al.
and wireless communication technology, distributed information processing technology [1].
Although WSN has been used in the fields such as traffic management, environmental mon-
itoring etc, the limited energy still is an important factor for WSN’s finite application. So it
becomes a crucial target for WSN’s research to efficiently extend the network’s lifetime with
the limited resource. Topology control (TC) is an important energy-saving technology [2],
because TC can economize energy by dispatching nodes’ transmitting power or scheduling
nodes’ sleep cycles. However, mostly existing topological structures are constructed via the
ideal wireless signal attenuation model. They don’t take into account the difference between
ideal application environment represented by ideal model and practical application environ-
ment. As a result, the actual topology is different from the designed one. Hence, it has a very
important significance for WSN to research TC algorithm based on practical application
environment.
Many researchers tried their best to avoid the defect that topology is too ideal to apply in
real environment, and obtained lots of achievements. Upon analyzing and summarizing the
existing algorithms (e.g. [3,4]), Wattenhofer put forward an extremely simple and strictly
local algorithm called XTC [3]. This algorithm doesn’t need the accurate location informa-
tion of nodes, and indicates link communication quality via one-hop neighbors’ Euclidean
distances. Consequently, XTC not only can be used in three-dimensional space but also
is suitable for practical application environment. However, XTC only qualitatively uses dis-
tance as the indicator of link communication quality. It does not take into account the additive
effect caused by the environmental difference in current network. To accurately assess the
link quality, Dyer et al did a thorough research [4]. The final result shows that, only under the
condition of the smaller standard deviation, has the link quality a bigger correlation with the
distance between nodes. In order to avoid representing link quality through the link’s length,
Schweizer et al. proposed a k TC algorithm in [5]. k TC uses rssi (Received signal strength
indicator) as link weight, employs the ratio of link weights as the standard to choose links.
rssi increases with the link quality enlarges [4], and is irrelevant with distance. In addition, it
can be detected at the receiving end in real time. rssi has no uniform metric if node’s trans-
mitting power is alterable, because it has a linear relation with transmitting power. Thus, the
designed topology is different from the one constructed by k TC in practical application.
The judgment condition which is used to construct topology results in the situation. This is
because the judgment condition can not exactly signify the communication situation of each
link. Unlike the k TC algorithm, the topology control strategy utilized in Ref. [6]ishow
to optimize the process of link selection. This algorithm prefers to choose a multi-hop path
rather than select the one-hop link whose energy is bigger than the multi-hop path. However,
this method makes topology a large delay, since the hop count is oversize. CTC is different
from the above algorithms, and charts a new course [7]. It employs nodes’ minimum trans-
mitting power to judge link communication quality, and adopts different strategies for each
link and each node. Thereby, this algorithm can partially solve the problem of link’s loss and
asymmetry. Nonetheless, CTC is only applicable to intensive network. Because it assumes
that the network still has strong connectivity, while all nodes adopt minimum transmitting
power. These above TC algorithms obtain good performances by choosing path or defining a
new indicator for link communication quality. However, these methods still can’t resolve the
problems existing in practical application, because they don’t take into account the unpre-
dictable real communication environment. As a consequence, there is still a big discrepancy
between the designed topologies and the actual ones.
With the deepening of the study, experts have already recognized that the real commu-
nication environment which described by path loss exponent is playing an important role
in topology research. To embody the significance of path loss exponent, LA-TPA analyzes
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