Offloaded Computation for QoS Routing in WSNs

Wireless Sensor Networks (WSNs) are commonly used to gather and transmit data to an application. These applications may have specific Quality of Service (QoS) requirements, such as delay, jitter, and packet loss, etc. In large networks, data transmission to a sink node requires multi-hop routing. It is important to understand how routing protocols designed for WSNs can meet QoS requirements that involve multiple constraints, typically end-to-end constraints. Our paper briefly analyzes a set of protocols, including the standardized Routing Protocol for Low-Power and Lossy Networks (RPL). In RPL, a Destination-Oriented Directed Acyclic Graph (DODAG) is used to transmit data from sources to a border router. The routing structure is computed based on an Objective Function, which may be defined for a single QoS metric and not reflect multiple constraints. An analysis of QoS-constrained routes is proposed to demonstrate that multi-constrained QoS routes from sensors to the sink do not always form an incast tree. Instead, a hierarchy, which is a generalization of trees, is the appropriate route. QoS-aware hierarchies can be implemented by a set of DODAGs. However, due to the complexity of computation, the protocols must be adapted accordingly to ensure practical implementation. We propose offloading the hard computation tasks to edge servers.