# Opportunities and Challenges for Error Correction Scheme for Wireless Body Area Network--A Survey
## 5 Review on ECS Methods on WBAN
### Forward Error Correction (FEC)
The paper proposed channel estimation using a pilot signal, but it does not provide details, including its impact on WBAN setting. The BER results of the BCH code and that of the proposed codes over different channels are standalone performances of those codes without considering the WBAN setting. The paper did not outline what type of decoding algorithms is used during the BER performance of convolutional code. As we discussed in Section 2.2, the performance changes significantly when decoding algorithm changes from hard-decision to soft-decision during decoding. The code rate of the proposed code is significantly lower when compared with the standard BCH code. The performance of ECC improved when the code rate is reduced. The code rate of 0.5 is convolutional code (2,1) for AWGN channel and the code rate is 0.4 for concatenated RS (63,51)-convolutional code (2,1) codes for Rician and Rayleigh channels for medical data to meet the desired QoS, which is significantly lower than the code rate of 0.8 for the BCH code. In general, the error control capability of the ECC is enhanced when the code rate is lower for any code. Therefore, to make fair comparison, the paper should have a presented BCH code with a similar rate. Therefore, the result is not a fair comparison when comparing the performance of code with different rates in the same setting. In [36], the authors simulate the performance evaluation LT codes in WBAN and compared the result with BCH codes with a comparable rate. The author claimed that the BCH code outperformed LT codes for a higher code rate, but the LT code outperformed the BCH code for lower code rate in several WBAN settings. The claim was developed from BER simulation results that considered SNR values from 0 to 40 dB. However, this is very unrealistic when WBAN is energy-constrained. Second, the BER simulation result of the coded (various rates) and uncoded system presented against SNR, which is not a fair comparison, as we explained in Section 2.2. The paper also presented PAR for both codes against hop distance ranging from 10 to 40 cm only. The range of hoping distance is very low when compared with the average size of the human body. However, the PAR reached almost zero when the hoping distance reached the upper value of hoping distance for all codes. The result indicated that the proposed code could provide a PAR of more than 0.9 in WBAN communication only around 10 cm hoping distance that is not suitable for average human body size. In [37], the authors conducted an initial investigation on the application of RS code on MAC layer data using real data of MIT-BIH arrhythmia databases. However, most of the paper content is a review of the IEEE 802.15.6 standard. The BER performance of shortened RS codes with varying code rate from 0.74 to 0.98 over the AWGN channel and fading channel is presented. However, the type of fading is not specified. The presented result and conclusion that are drawn in the paper are very generically related with coding principles but are not specific to the WBAN setting. In [39], the authors presented the Raptor code as an ECC for WBAN and compared its performance (in term of energy consumption versus distance) with BCH. The paper claimed that the energy efficiency of the proposed code is better than BCH for different types of fading channels, including Nakagami, Rayleigh, and Rician, when the distance between nodes is higher than 10 m. However, WBAN is network around a human body and the range of the distance between nodes in the network is limited to less than five meters in practical settings. In [40], the authors extended their work [39], where the result is compared with two more techniques: LT code and ARQ. These presented results are standalone performance without considering the WBAN setting. The authors introduced a static XOR (logical operation) based architecture with three relays selection for WBANs in [41]. The BER results that are presented in [41] are against SNR instead of \(E_{b}/N_{0}\).