ENERGY EFFICIENT AND RELIABLE COMMUNICATION IN IEEE 802.15.6 IR-UWB WBAN Aravind M T Dept. of ECE National Institute of Technology Calicut, India aravindmt2014@gmail.com Lillykutty Jacob, Senior Member, IEEE Dept. of ECE National Institute of Technology Calicut, India lilly@nitc.ac.in Abstract—This paper presents an exhaustive study on the use of one-relay and two-relay cooperative communication schemes and 2-hop communication scheme for improving the energy efﬁciency and reliability of ultra-wideband based wireless body area networks (UWB WBANs). Various investigations have been performed to study the impact of the parameters like packet size, hop distance, transmit power and channel error rate on the energy efﬁciency and reliability. An optimal packet size is obtained for the maximization of energy efﬁciency for both on-body communication and in-body communication. The analytical and simulation results show enhanced reliability with cooperative communication than direct communication and 2-hop communication, for all values of source to destination distances. The results also depict a threshold behaviour for energy efﬁciency which separates the hoplength for direct transmission from the hoplength where cooperation and 2-hop communication will be useful. The simulation results reveal that if the channel conditions are poor, when the source to destination distance is larger than the threshold value, 2-hop communication gives higher energy efﬁciency compared with direct and cooperative communications. Index Terms—Ultra wide band, Wireless body area networks, Energy efﬁciency, IEEE 802.15.6, Incremental cooperative relay- ing, Optimum packet size, Reliability. I. I NTRODUCTION There is a huge necessity that future health care systems aid proactive health care managements. The wireless body area network (WBAN) concept comprises tiny intelligent sensors implanted on and/or in the human body to acquire critical physiological data which are further to be monitored by doctors or health practitioners. Approval of IEEE 802.15 TG6 physical (PHY) and the medium access control (MAC) speciﬁcations for WBAN was made in 2012 [1]. The domain of applications of UWB communication (large data rate-short distance or low data rate-long distance) is constrained to a great extend by the restrictions on the transmit power(i.e; the power limit is below 0.5mW). The transmit power constraint implies that multiple low energy UWB pulses need to be combined to transport one bit [2]. Higher number of pulses per bit implies lower data rate and, in turn, larger trans- mission distance. The interference of UWB signals on narrow- band radio systems is very low because of its low power spectral density (PSD). The reduced size, cost and weight of the UWB transceivers due to the absence of modulator, demodulator, etc and the reduced power consumption of UWB systems make it preferred choice for WBANs. However, UWB communication is a ﬁeld that needs further investigation. To combat the multipath fading, and hence to improve the link reliability and throughput of WBANs, various techniques are presently being considered, of which, cooperative com- munication proposals are focussed more [3] which use relay mechanisms to improve the communication link efﬁciency. The traditional cooperative relaying mechanisms cause a wastage of the channel resources since the relays always forward the signal without taking into consideration the channel conditions. Usage of the orthogonal channels for communication by the relays and the source causes extra resources even though relaying is not required when successful direct communication is possible. The conservation of the channel resources form the main objective of incremental relaying schemes. If the source-to-destination link SNR is sufﬁciently high, an ack from the destination could be used to indicate that there exists a successful direct transmission link, and relaying is not needed [3,4]. In the case of an incremental relaying technique, the destination processes only a single signal at a time, and hence no need of co-phasing and combining, leading to simpliﬁed receiver units. Cooperative and multi-hop communications have been considered as effective methods to enhance the energy efﬁciency of BANS [5-6].The work in [5] proposes a model for energy efﬁciency in 2-hop communication and an optimal packet length to attain the maximum energy efﬁciency. In [6] authors propose a relay selection procedure for energy efﬁcient cooperative communication. However, these works are for NB PHY layer. Packet length is an important parameter which inﬂuences the reliability of transmission and energy consumption of a communication link. A long packet increases the packet error probability and thereby wasting the energy associated with the unsuccessful transmission. For smaller packet size the rate of transmission success is supposed to be increase, but short packet will lessen the system efﬁciency because of the packet overhead. In [4] the authors consider packet size optimization for the incremental relay based cooperative communication in WBANs based on NB PHY layer. The author in [7] also deal with the packet size optimization to enhance the eneygy efﬁciency for NB PHY layer. In[8] the authors study frame length optimization for UWB WBAN. The packet success rate corresponding to both PHY modes deﬁned in the standard are derived. The work in [9] presents the use of 1-relay cooperative communication for optimizing the frame length in IEEE 802.15.6 UWB WBAN. Different from the above works, in this paper we perform en- ergy efﬁciency and reliability analysis of two-relay cooperative and two-hop UWB WBANs and compare their performance with direct link and one-relay UWB cases. For all four cases, we study the impact of packet size, hop length and packet error rate on reliability and energy efﬁciency. The rest of the paper is organized as follows: Section II describes the system model and the schemes that are analyzed. Section 978-1-5386-5314-2/18/$31.00 ©2018 IEEE 2352