Actor-actor communication is an important part of the functioning of wireless sensor-actor networks and enables the actor nodes to take coordinated action on a given event. Owing to various reasons such as actor mobility and low actor density, the actor network tends to get partitioned. The authors propose to use the underlying sensor nodes, which are more densely deployed, to heal these partitions. In order to maximise the utilisation of the limited energy available with the sensor nodes, a new routing protocol for actor-actor communication using directional antennas on the actor nodes is proposed. The authors contribution is threefold. First, using simulations they show that the problem of partitioning in the actor networks is significant and propose an architecture with directional antennas on actor nodes and sensor bridges to heal these partitions. Second, they identify the routing problem for this architecture based on a theoretical framework and propose centralised as well as distributed solutions to it. Third, they develop a routing protocol based on the distributed solution and show, using network simulations, that the proposed protocol not only heals the network partitions successfully, but also achieves high throughput and fairness across different flows, in addition to maximising the network lifetime.

In Wireless Sensor and Actor Networks (WSANs), effective Actor-Actor Communication (AAC) is an important requirement for the timely responses to events reported by the sensors. However, due to scattered nature of events, mobility of actor nodes, and low density of actor nodes, the network of actor nodes tends to get partitioned frequently. To provide effective AAC in such situations, the energy-constrained sensor nodes located between the partitioned actor nodes need to be utilized. This solution for healing the actor network partitions should involve minimal use of the sensor nodes so that the network lifetime is maximized. In this work, we propose an energyefficient Actor-Actor Reliable Transport Protocol (A 2 RT) for WSANs with actor nodes equipped with directional antennas and dual radio interfaces. Our proposed transport protocol consists of a transport wrapper and a dynamic priority scheduler. Using simulations, we show that our transport wrapper achieves high reliability with minimum retransmissions both under static and dynamic network topology conditions. The results also show that the traffic scheduler of our protocol helps to achieve the goals of real-time delivery by maximizing the number of packets that meet the delay constraints.

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