# Opportunities and Challenges for Error Control Schemes for Wireless Sensor Networks: A Review
## 5 Review on ECS Methods on WSN
### Fec
#### 5.1.2 FEC for WSN
In [84], the paper considers three scenarios: uncoded using ARQ, intermediate nodes are not decoding the packet and Viterbi decoding and encoding for inner code applied at each intermediate node for results presentation. There is confusion between interleaver size and symbol size during result presentation and discussion. However, how inner and outer code is used in SCCC during BER simulation is not clear as results are presented for outer codes only and inner codes only. The final simulation result of BER versus SNR shows that BER lies between 0.3 to 0.5 which is a high BER for any communication system. However, the paper claims that the proposed SCCC can correct most packets with 2 to 5 hops WSN at low SNR that is contradictory to BER results presented in the paper. Another paper presents error pattern analysis WSN 2.4 GHz channel using hardware implementation of CC2520 RF transceiver as node [85]. The experiment is conducted in several settings over the range of 0 to 60 m between two nodes, but there is no clarity whether or not LOS exists between the nodes. The experimental results indicate that there is more burst errors than random errors, but the rate of occurrence of burst error is very small when burst length exceed 50 bytes. Then, the paper introduces shortened RS (114, 50) code derived from RS (255, 191) to tackle bursty errors based on the experimental result. Then, PER versus distance and RSSI is measured using RS code and uncoded system using an experimental setting. [PERSON] et al. claim that the proposed RS code is able to improve transmission distance by about 5 m compared with WSN without error correction at PER of \(10^{-3}\). The results from PER versus RSSI showed that the RSSI can improve by about 13 dB by using error correction at the same target PER of \(10^{-3}\) compared with WSN without error correction. However, the cost of encoding, decoding, transmission and reception cost of extra bits due to redundancy is not considered during this result presentation. Therefore, the results from this paper is very obvious as PER is reduced due to introduction of error correction. In [86], [PERSON] et al. analyse the impact of BCH and RS codes with different error correction capabilities on characteristics distance in a linear multi-hop model with equal hop distance. The paper considers two cases: decoding at all nodes and only at the destination node over all nodes transmitting and a single node transmitting situations. The characteristic distances for those scenarios are analytically calculated in terms of energy consumptions by different factors. Then, the paper presents results as characteristic distance versus bit error probability for those scenarios. However, the bit error probability calculation in the paper is generic in terms of average SNR not \(E_{b}/N_{0}\). Therefore, the bit error probability does not incorporate any effect of error correction capability of BCH and RS codes. The paper concludes that hop distance increases when all intermediate nodes are decoding in both scenarios. However, there is no impact on hop distance when decoding is only done in destination node in both scenarios. In [87], [PERSON] et al. introduce use of LT code for wireless multimedia sensor network for image transmission. The paper evaluates peak SNR and structural similarity index metrics for RS and LT codes considering a binary erasure channel with different erasure probability. The simulation results based on MatLab indicate that LT codes are significantly better than RS code. However, there is a lack of clarity about code rate of those codes and energy efficiency analysis between these codes. The summary of the review of FEC based ECS for WSN is presented in Table 3. One of the key findings from the review is that the use of a realistic network model to represent WSN in a practical setting is lacking. As the distance between nodes in WSN in a practical setting is not equal, a modified multi-hop WSN model is a more realistic network model.