12
Conclusions and Future Trends
12.1 Conclusions
Network-on-chip (NoC) has evolved as a viable solution to the
communication problem between cores in a system-on-chip (SoC). System
cost, in terms of area, delay, power, and so on, has contributions from both
computation and communication requirements. Individual cores can be
designed efficiently to make computation faster, but communication may
become a bottleneck. As discussed in all chapters, the solution is influenced by several factors. The first and foremost issue is the topology in
which routers are to be connected. While regular topologies, such as mesh
and tree, make the design process simpler with predictable link delay and
power consumption values, irregular application-specific topologies are
expected to produce better performance. Individual routers should be simple with modules, such as ports, routing logic, arbiter, and channel allocator. Design of routing algorithm plays an important role, as it has to be free
from deadlock and livelock problems, which may route in a shortest path
through the network. Performance of such a network is often evaluated
with the help of simulators and traffic generators. Apart from applicationspecific traffic, networks are often evaluated using uniform, self-similar,
hot spot, and other types of traffic. For regular topologies, cores of an
application are mapped onto individual routers using some mapping
techniques. The mapped core gets attached to that router and all communication to and from the core is made through that router. The mapping
problem is NP-hard; however, many heuristic strategies have been developed for the same. However, to achieve better performance, applicationspecific NoC architectures are evolved. Multiapplication NoC design calls
for a reconfigurable architecture, in which the same network resources
are reused for different applications. The power consumed by the NoC in
either case can be reduced using various strategies, such as encoding, serialization, and clock gating. A related issue is that of reliability of the system. Electromagnetic interference, synchronization failure, and soft errors
come up as challenges to a reliable system operation. Testing of such system requires testing individual cores, routers, and links.
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