# 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 this section, we review FECs introduced by research papers for general WSN. In [77], [PERSON] et al. present experimental results (packet drop rate, distribution of burst bit errors and distribution of burst packet errors) of several codes including two versions of SECDED and DECTED under outdoor and indoor environments. The nodes are separated 182.9 m apart and are in LoS in outdoor environments. However, the indoor setting of sensor nodes is not clear regarding LoS and distance between the nodes. The paper claims that both versions of SECDED are able to achieve packet drop rate to zero when nodes are 182.9 m apart and are in LoS in outdoor environments. The results for indoor settings are unclear. The reason for performance variation between SECDED (13, 8) and SECDED (30, 24) is clearly explained. However, the poor performance of DECTED is not clearly explained. Experimental results for one indoor setting (location three) shows that uncoded, SECDED (13, 8) and DECTED (16, 8) have zero packet drop rates, but SECDED (30, 24) has poorer performance than the uncoded system. The authors did not mention the reasons behind those results in the paper. In an experimental setting, [PERSON] et al. mention that the same packet is transmitted 5000 times, and it is not clear what types \begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Ref (Yr)** & **Proposed FEC for Uplink and Downlink** & **Application Scenario(s)** & **Result(s)** \\ \hline
[72] (05) & Downlink-CRC with ARQ (no FEC) and uplink-convolution code with Viterbi decoding & Slow fading channel & Comparison of power consumption of the proposed convolutional code against distance. \\ \hline
[74] (08) & Downlink-CRC with ARQ (no FEC) and uplink-RA code with SPA decoding & Wireless path loss model and AWGN channel & Comparison of power consumption between proposed RA code and convolutional code in single hop SAHS and RA outperforms convolutional code. \\ \hline
[75] (08) & Downlink-no specific discussion and uplink-iterative decoding using BCJR algorithm at base station and rate-1 encoding at energy-constrained sensor node & Line of Sight (LoS) and AWGN channel & Coding gain \\ \hline
[76] (09) & Downlink-no specific discussion and uplink-Turbo, repetition and convolutional code & Experimental setting is not clear & Experimental measure result of energy consumption (based on MICAz hardware) for uncoded, repetition code and modified turbo code. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: A review of FEC based ECS for SHAS structure. of bits on packets are transmitted. It is not clear whether there is any impact of data packets on the performance of specific codes or not. [PERSON] and [PERSON] examined energy efficiency of uncoded and BCH codes with different correction capabilities in multi-hop WSN considering different packet length [78]. The simulation is performed in a linear packet forwarding model where distance between end-node and sink is 100 m and considers a single-hop to 20 hops (with uniform distance between nodes) scenarios. The energy consumption model is based on [68]. Overall, the paper claims that communication using longer packets is more energy efficient than the shorter packet. In addition, [PERSON] and [PERSON] claim that the need for error correction decreases as the number of hops increases. Therefore, an uncoded system is more energy efficient than a coded system in densely populated multi-hop WSN. [PERSON] and [PERSON] extend their work of [78] to [79] to compare the performance of RS, BCH, and convolutional code with different error correcting capabilities. The paper claims that RS code is the most energy efficient among them. The efficiency of RS code with large error correcting capability is better than an RS code with small error correcting capability when the number of hops is less than 10. However, the efficiency is similar when the number of hops is more than 10.