Rainbow product ranking based relay placement and adaptive retransmission scheme for a reliable 802.15.4e LLDN

Industrial Wireless Sensor Networks (IWSNs) adopted for wireless factory automation demand highly reliable, robust and delay sensitive communications over an interference prone and harsh channel conditions existing in factory environments. IEEE 802.15.4e Low Latency Deterministic Network (LLDN) mode is the latest in IWSN standards which attempt to satisfy these requirements assuming controlled RF environment with frequency planning. However, realistic indoor factory environments suffer from interference as well as multi-path fading resulting in frequent packet losses, thereby affecting the communication reliability in terms of drop in overall Packet Delivery Ratio (PDR). To improve the reliability there are two important approaches, first cooperative diversity using relay nodes and second incorporation of Forward Error Correction (FEC) techniques, both of which are not available in the aforementioned standard. Hence, to enhance the reliability offered by 802.15.4e LLDN, we have proposed a two-fold solution in this paper. First an efficient and realistic relay node placement strategy based on Rainbow Product Ranking algorithm and second an Adaptive Retransmission scheme using selective cooperative diversity and Reed Solomon (RS) block codes.