본 논문에서는 의료용 in-body WBAN (Wireless Body Area Network) 시스템을 위한 GM (Group Manchester code) 변조 방식을 제안한다. 현재 IEEE에서는 WBAN 시스템을 802.15. TG (Task Group) 6로 지정하고 이에 관한 표준화를 진행하고 있다. 높은 전력 효율이 요구되는 WBAN 시스템을 위해 최근 표준화 그룹에서는 PPM(Pulse Position Modulation) 신호 간의 grouping을 통하여 전송률 이득을 얻을 수 있는 GPPM (Group Pulse Position Modulation) 변조 방식이 제안된 바 있으나, 기존 GPPM 방식은 복조 과정의 SNR 손실 및 gray coding의 부재로 인한 BER 성능 열화가 나타나는 단점이 존재한다. 따라서 본 논문에서는 PPM 보다 잡음 성능이 우수한 Manchester code를 기반으로, GM 방식의 BER 성능 최대화를 위한 복조 방식 및 turbo coded GM을 위한 LLR (Log Likelihood Ratio) 판정 방식을 제안하였으며, 다양한 성능 2 분석을 통해 제안된 방식의 우수성을 입증하였다.
In this paper, we propose group Manchester code (GM) modulation scheme for medical in-body wireless body area network (WBAN) systems. In IEEE, the WBAN system is assigned as 802.15. Task Group 6 (TG 6), and the related standardization is being progressed, Recently, in this Group, group pulse position modulation (GPPM), which can obtain data rate increase by grouping pulse position modulation (PPM) symbols, is proposed as a new modulation scheme for low-power operation of WBAN system. However, the conventional method suffers from BER performance degradation due to the absence of gray coding and its demodulation characteristics. Therefore, in this paper, we propose a modified GM scheme which groups Manchester code instead of PPM. In the proposed GM scheme, a low-complexity maximum likelihood (ML) demodulation method is employed in order to maximize the BER performances, Also, log likelihood ratio (LLR) decision method is proposed to employ the Turbo code as forward error correction (FEC), Finally, we verified that the proposed method has a good performance and is an appropriate scheme for in-body WBAN system through extensive performance evaluation.
