# A Cross-Layer Media Access Control Protocol for WBANs
## 1 Introduction  
Cardiovascular diseases (CVDs) have become the top killer, endangering human health [1], which brings a heavy burden to the healthcare systems of many countries. Sometimes, people even die without warning during sleep [2], and even young athletes experience sudden death caused by CVD. Obtaining correct diagnosis and prevention ahead of sudden cardiac arrest or death is generally preferable to in-the-field reanimation [3]. However, CVD has the characteristics of concealment, suddenness, harmfulness, and urgency, which increase the difficulty of disease prevention, diagnosis, and monitoring, posing challenges to the traditional medical system. A sustainable medical system must adhere to the simultaneous development of efficiency, quality, and safety. It is necessary to continuously research new technological methods to improve the effectiveness of medical diagnosis and treatment, improve the efficiency of medical services, and reduce resource consumption. For sports, traditional education methods rely on the experience of teachers [4]. Sustainable sports education should introduce new technological methods to evaluate athletes' training effects based on detailed and accurate data and develop targeted strategies. At the same time, it should ensure the health of athletes during training and prevent accidents such as sudden death caused by inappropriate exercise. The sustainable development of sports science requires the establishment of scientifically standardized and digitally intelligent training and assessment methods that can iterate and evolve. In fact, with increasingawareness, sustainable development has become a development strategy for numerous countries in human society. Whether it is in the fields of healthcare, sports, or education, optimizing the development models through technological innovation is necessary. Thanks to the advancement of science and technology, the integrated e-healthcare system provides an efficient way to resolve the above issues. Wireless body area network (WBAN) plays an important role in the e-healthcare system [5], as the integrated biosensors can collect and transmit vital human-centered data, such as electrocardiograms, temperature, heart rate, oxygen saturation, and posture. These data are then uploaded to the remote server to provide health assessment and exception warnings. Potential patients can be identified from a large population, diseases can be diagnosed and treated earlier, and the use of medical resources will be more precise and effective, which is of great significance for the sustainable development of the healthcare system. Meanwhile, the training of athletes will be more scientific and efficient with the help of WBANs, which is helpful for sustainable smart sports development. A WBAN is a wireless network composed of a coordinator and a set of miniaturized sensors. There are many challenges associated with WBANs that need to be solved and optimized. Firstly, energy is precious for sensors since their battery size is limited; thus, energy efficiency should be maximized to prolong the network lifetime. Furthermore, Quality of Service (QoS) should be satisfied, and the heterogeneity of data and the dynamic network environment should be considered when designing network scheduling schemes. Moreover, wireless resources should be managed efficiently to reduce transmission collisions and idle listening. MAC protocol [6], routing protocol [7], and power adjustment scheme [8] are usually optimized to solve the above problems. Existing related work has shown effectiveness in improving network performance. However, these works typically consider power adjustment and cooperative transmission separately, and the power adjustment process of nodes usually only takes into account the impact of channel conditions. There is a lack of consideration for the differentiated performance requirements of heterogeneous data transmission and the design of data loss retransmission mechanisms.