# 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
(residual BER and throughput) against \(E_{b}/N_{0}\) in [50; 56] in similar settings. Therefore, the comparison made in [51; 56] is not fair and not reasonable, as we discussed in Section 2.2. In addition, the simulation settings in the paper indicated that the channel model are considered as CM3 and CM4, the detailed discussion of how those channel models are adjusted in the simulation is not presented. Furthermore, the proposed scheme uses soft-decision Viterbi decoding that has a significantly higher decoding cost when compared with standard BCH decoding. However, the cost associated with the decoding complexity is not considered during the result presentation and discussion. The work presented in [52] is similar to [50], with slight variations and some additional work. The additional work performed in [52] is an energy efficiency evaluation of the proposed ECS that is based on [57]. The energy efficiency as a function of \(Es/N_{0}\) is presented for the proposed ECS and standard approach for data with different priorities (user priority 5 and 6). However, the energy efficiency evaluation of the standard approach i.e., IEEE 802.15.6 approach is presented without proper evaluation in the paper. The energy efficiency is presented as a function of \(Es/N_{0}\) that do not consider the overhead that is caused by the code rate of ECS. The simulation setting for the average case in [51; 56] and [52] is almost the same, but the residual BER of data with higher user priority has 2 dB coding gap between results in [51; 56] and [52]. However, the paper did not discuss discrepancy in the result, even if the main author of both papers is same. In [52], the paper presented residual BER and energy efficiency versus allowed delay for different values of \(Es/N_{0}\). The author concluded that the residual BER of the proposed scheme was improved for poor channel condition that is very predictable as the proposed scheme is using the complex decoding algorithm as well as lower code rate ECC when compared to the standard approach. In addition, residual BER and energy efficiency [52] are presented versus \(Es/N_{0}\) and the discussion also only refers to \(Es/N_{0}\) instead of \(E_{b}/N_{0}\) that do not incorporate overhead that is caused by ECS. Therefore, the presented result is not a fair comparison. The concepts that are introduced at [50] are also extended in [53] when considering multihop WBAN (refer to Figure 6). The concept of Weldon's ARQ operation is extended to two hops WBAN setting. The performance of the proposed scheme is compared with standard scheme (IEEE 802.15.6 approach) in terms of PER, energy information, and average number of transmission versus \(Es/N_{0}\) while considering the DBPSK and DQPSK modulation scheme. The paper claimed that the proposed scheme has better performance than the standard approach. However, the paper uses binary and higher order modulations as well as various code rates, but the results are presented against \(Es/N_{0}\) instead of \(E_{b}/N_{0}\). Referring to Equations (2) and (3), the results do not reflect the code rate and higher order modulation when they are presented against \(Es/N_{0}\). Therefore, the presented results do not consider code rate and higher order modulation during the result presentation. In addition, result is not considering the decoding complexity of soft decision Viterbi decoding during the result and discussion. In [54], the authors extend their previous work [50] when considering two types of access mechanism (random and schedule) in the MAC layer. The probability of successful transmission on PHY, MAC, and cross-layer (considering PHY and MAC) is derived mathematically. In the paper, the compared results are presented in terms of average number of transmissions and probability of unsuccessful transmission versus Es/N\({}_{0}\) for the proposed and standard method i.e., IEEE 802.15.6 approach. The paper claimed that the proposed scheme has better performance than the standard approach.