Performance analysis of LT codes and BCH codes in RF and FSO Wireless Sensor Networks

Free Space Optical (FSO) Wireless Sensor Networks (WSN) are immune to electromagnetic interference, license-free and are characterized by high bandwidth and ease of deployment. They face a major drawback in turbulent atmospheres. So, we consider hybrid FSO/RF energy-aware WSN with reliable data communication using ECC (Error Control Coding) methods. LT codes are a class of rateless codes used for recovering data from the transmitted symbols, which are prone to erasure. They are normally applied for packet recovery in high packet loss scenarios. In this paper, we implement LT codes for Forward Error Correction (FEC). We consider BPSK subcarrier intensity modulated FSO communication where a method of discarding weak symbols received, is employed with an optimal erasure zone as a pre-processing stage in LT decoder. We determine the optimal symbol-erasure zone and also impose an upper bound on BPSK threshold. The performances of LT codes and BCH codes are analysed for FSO and RF channel under different atmospheric conditions and link ranges. We consider energy consumption per bit as a performance metric for comparison. The proposed method for LT codes was observed to be more energy-efficient than BCH code in highly turbulent atmospheric conditions.