Scheduling for tandemly-connected sensor networks with heterogeneous link transmission rates
Ryota Kimura, Masahiro Shibata, Masato Tsuru · 2020
As a simplest sensor network topology, a tandemly-connected multi-hop wireless network model is studied, in which nodes are tandemly arranged and serially connected by unreliable lossy links. Each node generates a data packet in every one cycle period and forwards it bounded for either of two gateways at both ends of the network; the gateways can send the data to a server using a loss-free infrastructure. In such environments, packet losses often happen due to not only attenuation and fading but also interference among links, thus unscheduled packet forwarding schemes are inefficient and suffer from a low success ratio of packet delivery to the server. In our previous paper, we proposed a centralized scheduling to design a static time-slot allocation for redundant packet transmission based on the positions and packet loss rates of links to maintain a high success probability of delivering all sensor data. However, it only considered homogeneous links with the same transmission rate, and also it is not optimal in some topological conditions. Therefore, in this paper, we essentially enhanced it to adapt to heterogeneous links with different transmission rates and to topological conditions that are not covered by the previous scheme. Our scheme analytically derives an optimal static time-slot allocation and combines it with forward erasure correction (FEC) against packet losses based on inter-packet XOR coding. The results of synthetic simulation have shown the validity of the analytical optimization, the benefit of coding, and the issues hard to consider in analytical models as well.