Acknowledgment strategies for efficient asymmetric routing in energy harvesting wireless sensor networks

Energy conservation has been a primary concern in wireless sensor networks (WSNs), where long-term operations are often required in hard-reach environments. Due to unavoidable batteries replacement or replenishment, diverse energy harvesting techniques have been integrated with WSNs to overcome limited battery power and extend the network lifetime. However, variable transmission power levels caused by non-uniform energy harvesting rates can lead to asymmetric links. In this document, we propose weighted and lazy acknowledgment schemes and their combination to efficiently route sensory data to a sink over asymmetric links. The weighted acknowledgment (WACK) can differentiate multiple paths between data source and the sink by assigning multiplicative weights on the paths. The lazy acknowledgment (LACK) can assure reverse path by waiting for extended communication range. An asymmetric link aware backoff mechanism is also proposed to avoid data contention and collision. We compare the proposed schemes through extensive simulation experiments and their results indicate that the proposed acknowledgment strategies can be a viable approach in energy harvesting WSNs.