# Opportunities and Challenges for Error Correction Scheme for Wireless Body Area Network--A Survey
## 5 Review on ECS Methods on WBAN
### Harq
#### 5.2.2 Harq-Ii
\begin{tabular}{c} WBAN/IEEE 802.15.6/Cross layer/medical \\ and non-medical/AWGN \\ \end{tabular}  & \multirow{4}{*}{ \begin{tabular}{c} Residual BER \\ and throughput \\ \end{tabular}  } \\ \hline \multirow{4}{*}{[53] (016)} & \multirow{4}{*}{ \begin{tabular}{c} Convolutional code with \\ Weldon’s ARQ \\ \end{tabular}  } & \begin{tabular}{c} Multihop star network and single \\ WBAN/IEEE 802.15.6/Cross layer/medical \\ and non-medical/AWGN \\ \end{tabular}  & \multirow{4}{*}{\ \begin{tabular}{c} PER, energy efficiency \\ and average number of \\ transmission \\ \end{tabular}  } \\  & & \\ \cline{1-1}  & & One hop star network and single & \multirow{4}{*}{
[54] (017) & \begin{tabular}{c} Convolutional code with \\ Weldon’s ARQ \\ \end{tabular}  & \begin{tabular}{c} WBAN/IEEE 802.15.6/Cross layer with \\ different access techniques/medical and \\ non-medical/AWGN \\ \end{tabular}  & \begin{tabular}{c} Average number of \\ transmission and \\ probability of \\ unsuccessful \\ transmission \\ \end{tabular}  \\ \hline \multirow{4}{*}{[55] (016)} & \multirow{4}{*}{\ \begin{tabular}{c} Convolutional code with \\ Weldon’s ARQ \\ \end{tabular}  } & One hop star network and single & Bit error probability, PER, \\ WBAN/IEEE 802.15.6/Cross layer/medical & \multirow{4}{*}{ \begin{tabular}{c} Bit error probability, PER, \\ throughput, \\ residual BER, \\ \end{tabular}  } \\  & & \\and throughput performance versus \(E_{b}/N_{0}\) over AWGN channel for the proposed and conventional method i.e., use of selective-repeat ARQ. The paper claimed that the proposed scheme is having better performance than the conventional method. The code rate is adaptive in the order of 7/8, 5/6, \(\%\), \(\%\). In [49], the results are presented in terms of residual BER and throughput performance versus \(E_{b}/N_{0}\) for the proposed scheme. However, no comparison with any other results is presented. The paper [49] claimed that IEEE 802.15.6 CM3 is used during the simulation, but CM3 covers different types of channels (refer to Table 3), such as LOS and NLOS. The paper did not outline what type of specific channel has been used during the simulation. The residual BER and throughput performance versus \(E_{b}/N_{0}\) for the proposed scheme, but with no comparison with any other result is presented. The adaptive code rate of convolutional code [50] and Reed-Muller code [49] are considered during the simulation, but how \(E_{b}/N_{0}\) is evaluated during the simulation is not clear in both papers. Furthermore, the papers did not outline the types of decoding algorithm used in during the channel decoding that is also key factor for energy-constrained node in WBAN. The concepts introduced at [50] are extended in [51; 52] when considering interference from the multiple WBAN environment. Two cases are considered in multiple WBAN environment: average and worst case. In average case, interfering WBANs are uniformly distributed within three meters from the objective WBAN, whereas interfering WBANs are closely placed to the objective WBAN in the worst case. In this paper, the compared results are presented in terms of residual BER and throughput performance versus \(E_{s}/N_{0}\) for the proposed and conventional methods i.e., IEEE 802.15.6 approach. In the proposed scheme, both types of data (user priority 5 and 6) is using the convolutional code with HARQ-II and code rate varying from 8/9 to 1/6, but with a different number of maximum retransmission according to user priority of data. In the standard approach, data with user priority 5 using BCH (63,51) with code rate 0.8, but data with high priority uses BCH (126,63) with a HARQ-II i.e., code rate of 0.5 and lower. The results (residual BER and throughput) are presented in [51; 56] is against \(E_{s}/N_{0}\) instead of \(E_{b}/N_{0}\). Consequently, the results do not take the code rate in to consideration i.e., do not consider the overhead caused by ECS. However, the same authors presented the results  
Figure 8: Block diagram for multiplexing [50; 56].