ULP systems in WS&AN: Combine the nJ/bit target with highly efficient connectivity

Wireless Sensor and Actuator Networks (WS&AN) currently face their actual deployment challenges. Simple point-to-point RF communications metrics remain focused on active modes peak power consumption and communication duty cycles. But, once RF links have to set themselves into mesh networks, complex interactions between RF nodes arise and various metrics must be taken into account. Here starts an optimization work implying cross-layer interactions. Low power PHY layers have to be implemented in such protocols avoiding any retransmission, and involving relaying. Thereby an efficient management of resources in use relies on a protocol stack, based on a lightweight operating system, including a mandatory neighbor discovery and network management process, and maintaining the communication link whatever the environment through relay operations. This paper exhibits resource roles and balance the budget link with relay benefits for power consumption saving from large Wireless Sensor Networks to small Body Area Networks.