Image Processing Reference
In-Depth Information
Nodes per cell
10
0
0
WISA
BT
WLAN
Zigbee
Enocean
100
10
Node
density
per m_
Real-time
limit (1/ms)
1
0.1
10
1
1000 100
10
10
1
0.1
Energy/bit with retransmitts (mWs)
FIGURE .
Visualization of comparison for the most important requirements in discrete factory automation
(empirical, mind logarithmical scale). (From Scheible, G., Dzung, D., Endresen, J., and Frey, J.-E.,
IEEE Ind. Electron.
Mag.
,,,.Withpermission.)
It is worth reminding that generally a smaller range allows a higher node density, due to lower
interference between cells. A low range is typically acceptable in factory automation, where a given
base station needs only to provide coverage for a manufacturing cell.
For technologies such as Enocean, ZigBee, and WLAN a low failure probabilities are not generally
possible due to the impact of, e.g., a moving environment in machines within their long range
r
(see Table ./II). Therefore the figures have been put in parentheses. Figure . visualizes the
achieved match of performance of WISA compared to the requirements and the discussed competing
technologies.
Itshouldbenotedthatdespitetheempiricalapproach,itisnotchangingthepicturealot,ifa
certain value would be differing by a factor of two, due to the logarithmic scales chosen on each of
the axes.
The characteristic figures defined in Chapter coexistence can be used to help practically judge
the coexistence behavior of the different in factory automation-used systems/technologies. To do
this, a fictive real-time system with a TDMA approach as implemented in WISA on an IEEE..
physical layer has been assumed implemented with the different physical layers of IEEE...-
based systems (Zigbee, WirelessHART) and as comparison WLAN (IEEE. g). To calculate a duty
cycle for frequency usage, it has been assumed that nodes should be covered as fast as possible,
an application cycle time of ms (e.g., programmable logic controller [PLC]) has been assumed, in
which all nodes should transmit one telegram correctly.
Table.showstheassumedrealizationsandthevaluesusedtocalculatethecharacteristicigures.
For the . PHY, it is visible that the resulting TDMA frame of ms would be much larger as the
anticipated applications cycle time of ms; therefore, . would not be practically usable with such
