Historically, neural
network models have been characterized by intensive processing, producing
and consuming large amounts of data, leading to either parallel and/or
distributed computation [
SN20]. In general,
workstation environments have been sufficient in processing smaller neural
networks having no more than a few hundred "simple" neurons. However, neural
networks consisting of thousands or millions of neurons and connections
among them can require many hours of simulation, as in the case of the
retina model [
SN21] consisting of more
than 100,000 neurons and half a million interconnections. Considering that
neural networks processing is based on differential equations, it takes
many cycles to generate meaningful output. These cycles are applied to
each neuron in the model, with input and output transmissions varying depending
on the number of interconnections among neurons. This gets even worse if
we consider, as shown in Figure 2, that an independently built model, such
as the retina, can then be part of a larger model, having many such interconnected
modules. Thus it is crucial to reduce processing time, something that is
possible if having access to high-end computers such as supercomputers
or through a distributed network of inexpensive workstations. In general
parallel environments have been harder to develop and program, thus making
workstations a much more accessible solution. It should be noted that providing
a powerful processing environment as part of the actual robot would mean
having robots the size a regular vehicle, something that would make research
on robotics much more expensive and harder to carry out. Thus, most of
the robot's intelligence is remotely provided by a single computer in the
case of smaller programs, or a network of computers in our case. In such
a way, we have developed a distributed NSL/ASL architecture, which will
serve as basis for the project [
SN22].
The general approach in the distributed environment is to process each
neural level module in a different machine, while schema level modules
are assigned to the machine with the corresponding neural ones [
SN23].
An important aspect in processing of schema and neural modules involves
the use of different temporal scales, something that in distributed system
requires additional considerations [
SN24].
Since many biological models, in particular those previously mentioned
and as the one shown in Figure 2 involve visuomotor coordination, an additional
constraint in processing is the requirement of real time video. This represents
two separate restrictions, one on the wireless network connected to the
camera on top of the robot and the second one in terms of the Internet
network that must process the video signal in an efficient manner. The
attainable image frequency rate depends on:
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The resolution of the camera .
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The bandwidth of the wireless network (including image compression considerations).
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The Internet2 bandwidth.
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The sophistication in object recognition.
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The distributed NSL/ASL processing efficiency.
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The actual model complexity.
There are additional factors affecting the system, in particular those
related to the QoS (
quality of service) and mobility of the robot.