Research On Reliability Of Data Link Layer In Ultrasonic Body Area Networks

Body area networks(BANs) is a kind of biological sensor network deployed on the body surface or implanted in the body. It belongs to a branch of wireless sensor networks(WSNs) and has broad application prospects in the fields of biological medicine, sports and military training. BANs is composed of a series of micro sensors with many built-in wireless communication modules, which have the characteristics of miniaturization, low power and implantation. In addition, with the rapid development of science and technology, BANs has made great progress in the field of health information, such as health warning, disease diagnosis, medical treatment and so on.Wireless communication technology is one of the main research directions in the field of BANs, and the transmission medium is the bridge and link of the information transmission in the wireless communication system. Particularly, there is a higher requirement for the choice of transmission medium in the health sector field. Traditional BANs uses radio waves as the transmission medium to transmit data, thus, it has the following problems:1) Because the radio waves can produce electromagnetic radiation, the electromagnetic pollution is bound to harm human health, so it is contrary to the original intention of BANs application in health care.2) In the medical environment, the signal power of the radio waves is very strict, which also restricts the application of radio communication in BANs.3) In the complex environment, the signal attenuation is serious, and even cannot normally communicate sometimes, which affects the reliability of data communication.In view of the above questions, this paper uses ultrasonic instead of radio wave in BANs, and forms a kind of network which takes ultrasonic as the transmission medium, named as ultrasonic body area networks(UBANs). On this foundation, an ultrasonic communication system is designed and implemented in this paper, and the system can communicate on the body surface in point to point mode. The focus of this paper is to study the reliable communication strategy suitable for UBANs environment. Therefore, this paper proposed two adaptive error control schemes which are based on UBANs. The first scheme is a UBANs adaptive error control strategy based on ultrasound intensity. This strategy takes ultrasound intensity as the threshold, and dynamically selects automatic repeat request(ARQ) or hybrid automatic repeat request(HARQ).The second one is a UBANs adaptive error control strategy based on hidden markov model(HMM). This strategy uses HMM to predict the bit error rate, and dynamically selects ARQ or HARQ based on the threshold. The feasibility and practicability of the strategies are proved by experiments. Moreover, we may find that the new strategies are better than the traditional ones by comparing the transmission success rate, energy consumption and other indicators. In conclusion, this research has reached the desired goals.