wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

11-6 Industrial Communication Systems
• Centralized processing: The network may lose the reliability in this regard.
• Power depletion of centralized hub is more as compared to heterogeneous sensing nodes. This
results in uneven network power balance.
11.3.3 Multitier Architecture
The right-most sensor cloud represents the multitier architecture. It comprises high- and low-end video
sensors, video processing hub, and scalar sensors. The low-end video sensors feed the gathered multimedia
content to the central video processing hub for localized processing of the multimedia information
and same is true for the scalar sensors as well. The high-end video sensors gather information from
the surroundings (high resolution) and from the video processing hubs, and relay the processed data
wirelessly to the gateway for storage or to the sink. In this case, the resource-constrained scalar sensors
are responsible for performing simpler tasks such as measuring scalar physical measurements while
resource-rich video sensor or multimedia nodes are responsible for complex tasks. In this architecture,
the storage and the data processing can be performed in the distributed fashion at each different tier.
The multitier architecture offers considerable advantages with respect to single-tier architecture:
• Single-tier configuration is used when power efficiency is required.
• Second-tier and third-tier are used when reliability is of major concern.
• Intelligent usage of nodes at each tier has the potential to reconcile the conflicting goals of energy
efficiency and reliability and overcome the drawback of homogeneous single-tier networks.
• Intelligent node placement can enable usage of high-power nodes at higher tiers only when
required with a wake-up mechanism, resulting in energy benefits.
• Coverage of a region with nodes from multiple tiers leads to availability of extra sensing and computation
resources, resulting in redundancy benefits.
• Better scalability, lower cost, and higher functionality.
The disadvantages include the following:
• Special consideration should be put for inter-tier and intra-tier communication.
• Synchronization among various tiered nodes is a very difficult task.
11.4 WMSN Hardware
The recent advances in complementary metal-oxide-semiconductor (CMOS) camera technology and
audio-capturing devices have taken WSN to the next level, i.e., WMSNs. In this section, we will discuss
some of the existing video sensor nodes. The video sensor nodes, or more specifically WMSN nodes, are
broadly classified into three different classes, based on the video-sensing node’s capability:
1. Low-resolution WMSN motes
2. Medium-resolution WMSN motes
3. High-resolution WMSN motes
11.4.1 Low-Resolution WMSN Motes
Low-resolution WMSN motes comprise CMOS camera and processing module (also named CMOS
imaging sensor), thus eliminating the need of several processing chips required by the traditional charge
coupled device (CCD) technology. Cyclops [RIGWES05] is an electronic interface between a CMOS
camera module (CMOS Agilent ADCM-1700 common intermediate format (CIF) camera) and a wireless
mote such as MICA2 [CM08] or MICAz [CMZ08] and contains programmable logic and memory
for high-speed data communication. The MCU controls the imager, configures its parameters, and performs
local processing on the image to produce an inference. Since image capture requires faster data
© 2011 by Taylor and Francis Group, LLC