Cryptography Reference
In-Depth Information
Figure 1.6. WSN Protocol Stack
it is difficult to achieve high end-to-end link reliability compared to traditional
wireless networks. In addition, the transport layer performs fragmentation of
sender data and reassembly of received data frames.
Network layer: The network layer's primary goals are to perform routing opera-
tions and self-configuration. It is responsible for link failures and provides regu-
lar updates to neighboring nodes. However, assuring network connectivity at all
times is a major challenge due to dynamically changing network topology. The
routing protocols in WSN are very different from traditional routing protocols
because of the need to optimize network life by performing intelligent routing.
Data link layer: The data link layer is an interface between the network and
physical layer. It is further subdivided into two modules: Medium Access Con-
trol (MAC) and Logical Link Control (LLC). The MAC module plays a critical
role in conserving network life by efficiently allocating medium access to the
contending nodes. The LLC is on top of the MAC layer and is responsible for
cyclic redundancy check (CRC), sequencing information and adding appropriate
source and destination information.
Physical layer: The physical layer is responsible for converting digital bits into ana-
log symbols and vice versa. It involves modulation and demodulation, frequency
selection, power control, and symbol synchronization. WSN usually operate in
frequencies ranging from 915 MHz to 2.4 GHz. It is recommended to use a
lower-frequency band, as there is higher attenuation when operating in higher-
frequency bands. However, with the limited availability of the bandwidth in the
lower frequencies, WSN is forced to operate at higher frequencies. The environ-
ment in which sensors are operating plays a major role in signal attenuation. Thus,
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