###### Abstract  
The performance of a quality of service (QoS) control scheme in a multi-hop wireless body area network (WBAN) based on the IEEE Std. 802.15.6 is evaluated. In medical Internet of Things systems, WBANs are an important technology. In a previous study, an optimal quality of service control scheme that employs a multiplexing layer for priority scheduling and a decomposable error control coding scheme for WBANs were proposed. However, the two-hop extension supported by IEEE Std.802.15.6 has not been considered. Here, the two-hop extension is applied. Then, the packet error ratio, number of transmissions, and energy efficiency of our previously proposed system are compared to a standard scheme under several conditions. Also, novel evaluations based on communication distance are conducted. Numerical results demonstrate that our proposed scheme, in which coding rates change relative to channel conditions, outperforms standard schemes in many aspects. In addition, those systems show the best performance when the communication distance of the first hop equals that of the second hop. In addition, the above result is theoretically clarified. wireless body area networks; multi-hop; IEEE802.15.6; error controlling; communication distance; QoS 2018 18 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3969 3970 3981 3969 3969 3971 3969 3982 3983 4984 4  
to them). In WBAN systems, a wearable vital sign sensor node can include various types of sensors with different data rates. In addition, the allowable communication error ratio and delay depend on the application. IEEE Std. 802.15.6 aims to provide an international standard for low power, short range, and extremely dependable wireless communication within the surrounding area of the human body, supporting a vast range of data rates [14]. Additionally, IEEE Std. 802.15.6 defines eight user priority levels. Quality of Service (QoS) control must ensure that different data types are communicated effectively and efficiently. Therefore, optimal QoS control for input data is an important feature in sensor data transmission procedures. To address this requirement, an optimal QoS control scheme that employs a multiplexing layer for priority scheduling and a decomposable error control coding scheme that adapts to varying channel conditions or QoS requirements have been proposed [20; 21; 22]. Here, the target WBAN consists of a wearable sensor device that includes multiple sensors whose output data are transmitted using a common medium access control (MAC) and the physical layer (PHY). In those studies, simulations and a theoretical analysis were performed to evaluate the performance of the proposed system by comparing it to an IEEE Std.802.15.6-based system [20; 21; 22]. Note that IEEE Std. 802.15.6 supports a two-hop extension. In this study, the performance of an error control scheme for a multi-hop WBAN based on IEEE Std. 802.15.6 is evaluated. Specifically, the packet delivery failure ratio (PDFR), number of transmissions as a replacement for delay, and energy efficiency which is throughput considering energy consumption of our previously proposed error control scheme and IEEE Std. 802.15.6 are evaluated relative to this standard's two-hop extension [20; 21; 22] like under multi-path fading channel of ultra-wideband (UWB) PHY. The main contribution and novelty of the manuscript are as follows:  
1. The performance of our previously proposed QoS control scheme is improved by appropriately determining the coding rate using channel estimation. With this improvement, data packets can be relayed to the hub with a small number of transmissions even when the maximum number of retransmissions is limited by a two-hop extension. 2. Novel performance evaluations are conducted as a function of the distance between transmitter and receiver assuming a real environment, which were not considered in our previous work [20; 21; 22].