## 1 Introduction
Many of the aforementioned HCWSN requirements (e.g., reliability, routing, node mobility, _etc._) have not yet been adequately addressed in a holistic manner by the sensor network community, thus leaving a gap between the existing WSN technologies and the specific requirements. For example, some research has directly addressed WSN reliability concerns by performing an evaluation of efficient and reliable protocols for fixed-power sensor networks [12]. However, the evaluated protocols are not designed to support multicast, mobility, or interference-mitigation. In [13], the TinyOS [14] version of Adaptive Demand-driven Multicast Routing (ADMR [15]), TinyADMR, is employed as the multi-hop routing protocol for CodeBlue, a prototype medical sensor network platform. The results from the experiments offered the following insights regarding the use of a multicast routing protocol in a real life WSN: (1) multicast routing in CodeBlue helps to mitigate the effects of bandwidth limitations. (2) ADMR deals gracefully with node movement for mobility rates typical of moving patients. (3) Background traffic and multiple paths do not adversely affect the packet latency, and (4) redundant packet transmissions increase the PDR. To further build upon the lessons learned from the extensive experiments executed of TinyADMR in CodeBlue, we extend our survey of routing protocols to feature other routing protocols that have been successfully implemented into a HCWSN prototype. By surveying a multitude of different routing protocols optimized for operation in health care applications, we can work closer towards the ultimate goal of producing an effective, efficient, robust, reliable communication layer for HCWSNs. Energy efficiency is an underlying fabric to the success of deploying WSNs. A significant proportion of energy consumption can be tied to the medium access control (MAC) layer, where energy consuming functions such as idle listening, overhearing, collisions, protocol overhead, and over emitting take place. Like any other application, health care specific applications require an energy efficient MAC protocol to ensure continuous operation along the lifecycle of a biomedical sensor. In this paper, we explore a number of MAC protocols that may meet the requirements of a HCWSN. Specifically, we focus our literature survey on CSMA-based protocols because they generally do not require slot synchronization and slot assignment, resulting in very good scalability. In addition to energy efficiency, reliability is also paramount to the success of HCWSNs. While redundant transmissions in the form of retransmissions have long been used as a technique for improving reliability, network coding has recently emerged as a viable technology for WSNs. The use of network coding for improving reliability first originated in wired networks. With its success, network coding has been implemented in a number of multicast routing protocols and evaluated in mobile ad hoc networks (MANETs) with good results. Specifically, network coding has been shown to significantly reduce network overhead while also improving PDRs. Reliable transport protocols are also studied as a solution to attaining reliability because they aim to reinforce successful packet delivery in a hop by hop fashion or end to end fashion therefore facilitating the functional operation of reliability-driven applications. Therefore, we review reliable transport layer protocols and a network coding based protocol from the literature for possible integration into a HCWSN. Recently, [PERSON] _et al._[16] have published a literature review paper that highlights a multitude of promising healthcare applications and the challenges they pose for integration into a WSN. These challenges arise due to the scarce resource availability inherent of WSNs, and more importantly the requirement to deliver high quality medical data while also ensuring their security and communication privacy.