Interference-Fault Free Data Aggregation in Tree-Based WSNs

WSNs are often besieged with issues related to interference when transmissions of two or more closely located sensor nodes interfere with each other. This forces the data aggregating nodes to receive distorted, faulty or interference ridden signals, which severely affects the fidelity of data being aggregated. If such faults are not arrested at the source, interference laden transmissions or Interference-Faults pervade the entire WSN. On detection of such faults, the aggregating nodes keep demanding retransmission of data packets till interference-fault free data is successfully received and deciphered. This adversely affects the network traffic load. However, for want of information related to potentially interfering nodes, all efforts to determine an Interference-Fault Free Transmission (IFFT) data aggregation schedule have achieved very limited success. In a recent pioneering work, a Composite Interference Mapping (CIM) model to generate a comprehensive interference map for all nodes in the WSN was developed. In this paper, we use the CIM model, to generate an interference map for tree-based WSNs. We develop an IFFT-Tree algorithm that generates an IFFT aggregation schedule for all nodes in a tree structured WSN. We prove analytically that the aggregation schedule generated by IFFT-Tree algorithm is optimized and is interference-free. Two performance metrics are introduced to study the performance of the algorithm in maximizing the number of IFFT schedules and minimizing the number of time slots. The performance of the algorithm is validated through extensive simulation studies.