**12. Conclusions and future research**

This chapter presented the smart routing protocol for large-scale networks that enables for the deployment of wireless sensor networks (WSNs) in geographically distributed locations of interest. Smart routing is based on performance measure and energy optimization using cross-layer considerations of the protocol stack. We presented the performance improvement of smart routing over minimum power routing in these distributed networks to illustrate the benefit of the smart routing protocol for enabling next-generation commercial applications. By doing so, we also presented the impact of application criticality on performance and network lifetime. Applications that have high performance demands require greater resources and, as a result, have shorter network lifetimes; energy-conserving systems, on the other hand, allocate resources to prolong network lifetime at the expense of performance.

We also covered energy harvesting and its impact on resource allocation. We determined that, since sensors are able to operate at peak performance as long as sufficient resources are available, energy harvesting enables us to maintain this level of performance for a longer period of time. If the replenishment rate *rh* is greater than or equal to the consumption rate *rc*, the network is self-sustaining and can theoretically survive on its own.

Future research shall explore a number of areas to further the smart routing protocol:


which positions are known in the field. This reduces the dependency of the policy on GPS, until sensors equipped with GPS are made more readily available; and

• **Optimization Metrics**: Model additional performance metrics such as delay, and additional physical (PHY) layer parameters such as bandwidth and modulation.
