In Japan, much attention has been paid to NASH and NAFLD for the past several years and the prevalence of this disease entity has been estimated, and NASH is thought to be present in 10% of those who have fatty liver diseases. Other points out the prevalence of NASH in Japan as 6 to 8 hundred thousand patients. The last two or three decades have seen the evolution of Western-style life of near complete inactivity, energy-dense food choices and liberal fiscal resources to obtain them and other means to avoid physical activity. Moreover, what is increasingly apparent is that NASH and NAFLD is not a Western disease and many population groups in the Asia-Pacific region are particularly prone to type 2 diabetes. Thus, it is not surprising that NASH has increasingly been diagnosed in several regions in Asia including Indonesia, Malaysia, Philippines, Thailand and India.
The past few years have witnessed increased interest among researchers in cluster-based protocols for homogeneous networks because of their better scalability and higher energy efficiency than other routing protocols. Given the limited capabilities of sensor nodes in terms of energy resources, processing and communication range, the cluster-based protocols should be compatible with these constraints in either the setup state or steady data transmission state. With focus on these constraints, we classify routing protocols according to their objectives and methods towards addressing the shortcomings of clustering process on each stage of cluster head selection, cluster formation, data aggregation and data communication. We summarize the techniques and methods used in these categories, while the weakness and strength of each protocol is pointed out in details. Furthermore, taxonomy of the protocols in each phase is given to provide a deeper understanding of current clustering approaches. Ultimately based on the existing research, a summary of the issues and solutions of the attributes and characteristics of clustering approaches and some open research areas in cluster-based routing protocols that can be further pursued are provided.