# 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
The energy efficiency of convolutional codes is better than other codes only when the distance between nodes is more than 33 m. The uncoded system is more energy efficient than a coded system in densely populated multi-hop WSN i.e., when the distance between nodes is 5 m or less. In [67], the paper presents results from experiments of WSN using Mica2 node and TinyOS applications. The paper presents measured results of packet lost, corruption rate and cost of transmission against transmission distance for uncoded systems and coded systems with convolutional code using Viterbi decoding. The distance between nodes varies from 0 to 40 m, but it is not clear whether or not LOS exists between the nodes. The net cost of transmission for each packet using FEC and uncoded system is evaluated using Equation (20). [PERSON] et al. present error control analysis, decoding complexity and power analysis of several codes and sensor node in [69]. The error control performance of RS, BCH and convolutional code is presented in terms of BER versus \(E_{b}/N_{0}\) with different rates over AWGN channels [69]. These results are standalone performance of these codes. The paper measures encoding and decoding complexity in terms of number of slices required and power consumption in terms of dynamic power per bit during implementation of those codes in FPGA (Xilinx Virtex-E XCV200E6 CS144). The result indicates that the complexity of encoder and decoder of BCH and RS codes increases linearly as the number of parity bits increases. However, the complexity of Viterbi decoder increases very sharply as the memory order increases. The result also indicates that the encoder of convolutional and BCH codes are less complex than RS codes. Additionally, the paper measures power consumption in terms of power per bit of these codes in ASIC settings. In ASIC, power estimation is performed using Synopsys's design compiler and design vision using technology independent components. [PERSON] et al. claim that ASIC implementation consumes less power than FPGA for the same code. Therefore, ASIC implementation is further analyzed. Finally, the power consumption per bit incorporating encoding, decoding, transmission and receiver cost at sensor node using Equation (4) is presented for all codes with different code rates with the distance between nodes of about 22 m. The paper claims that power consumed by BCH and RS codes is less than uncoded systems. However, the power consumed by convolutional code with Viterbi decoding is more than uncoded system. Therefore, [PERSON] et al. claim that linear cyclic codes consume significantly less power than uncoded systems, and it is suitable for error correction on WSN. However, the paper presents power consumed after introduction of FEC, but there is no clarification on how it is measured. Additionally, the choice of using the distance between nodes of 22 m is not clear. In [15], [PERSON] and [PERSON] perform comparison analysis of ARQ, FEC and HARQ types I and II (FEC as both BCH and RS) schemes in terms of energy consumption, decoding latency. The paper claims that the selection of the error control scheme depends on physical architecture of WSN, node distance and expected reliability. [PERSON] analyzes error characteristics of channels for WSN using Mica mote and also simulates BER versus \(E_{b}/N_{0}\) and evaluate power consumption by several codes in [80]. The analysis for error characteristic of channel indicates that most errors are single bit or double bits error and burst error is rare. However, there is no clarity of the experimental setting such as how the channel measurement is performed and whether there is LOS or NLOS between the nodes. There is no clarity of how power consumption is evaluated or measured for several RS codes. There is a lack of clear connection between the energy model presented in the paper and power consumption presented for several RS codes. [PERSON] presents standalone BER simulation results for several codes including uncoded and several FECs.