## 1 Introduction
#### Emergency Scenario  
Consider a WBSN with sensors reporting data remotely to a medical center through a mobile device such as a smartphone with video conference capabilities. Under a stable health condition, the Personal Health Information (PHI) of the patient should be reported to the medical center every 5 min. However, occurrence of an emergency event (e.g., traffic accident, natural disaster, heart attack, _etc._) requires the reporting of PHI and video to be every 10 s, and the amount of data produced is incremented in a very short time. The scenario just introduced is an _emergency assistance scenario_, capable of saturating the WBSN, with different technological challenges including mobile computing, medical sensors, video technologies and communication for mobile healthcare (m-Health) systems [6]. In emergency situations, the integration of a WBSN and a smartphone can enhance the existing medical emergency procedures and minimize the possibilities of permanent injury or death. A basic WBSN-technology implemented in an emergency scenario is shown in Figure 2. It shows a body sensor network where a paramedic is connecting a patient. Sensors will communicate wirelessly to the mobile device and the mobile will capture parameters for subsequent delivery to the servers. Mobile networks help to reduce time and facilitate decision making in these circumstances. Exploiting the potential benefits of these networks can result in additional challenging issues. One of these challenges is the interference which is generated by the coexistence of different technologies working in the same place. Interference may occur in crowded places such as airports, theaters, stadiums and hospitals. Other relevant issues to be considered are: scalability, sensor deployment, sensor density, energy efficiency, emergency detection and response [7]. Figure 2: Wireless body sensor network communicating through a mobile phone. Under an emergency scenario, the smartphone is going to experience both high energy consumption due to the execution of multiple tasks, and serious degradation in performance due to tasks such as a highly intensive monitoring and video streaming. Thus, the remaining energy in sensors of a WBSN becomes as critical as that on the smartphones. Although emergency scenarios are infrequent (_i.e._, an average of 50 cases out of 10,000 [8]), these energy and performance issues represent an important technological challenge in terms of Quality of Service (QoS) assurance. In ZebranBAN [9], the authors addressed the efficient use of energy and performance improvement issues with the objective to support high-speed data transmission in future WBSN from the perspective of a heterogeneous network. This paper presents a survey of current trends in WBSN for emergency scenarios. Our paper also presents facts that play different roles for each medical scheme and have an impact on the network performance and the reduction of the WBSN lifespan. This paper also discusses issues about the medical emergency scenario such as WBSN architecture, recent studies in power efficient MAC protocols and the main communication protocols for m-Health. We also understand that efficient use of energy is the dominant factor in the design and implementation of protocols in wireless sensor networks for MAC/PHY and network layers in order to reduce power consumption and latency, and to increase throughput. An energy inefficient protocol may become the main source of energy waste [10]. Additionally, we introduce the fundamentals towards a definition of an optimization framework for the energy consumption on emergency scenarios. We also discuss communication and network protocols to improve performance of the WBSNs in terms of QoS. We also present relevant aspects such as: data compression and security of the medical information, and also the synchronization and joint transmission of this information with the video stream to enhance the network resources. In Section 2, we present a review of previous work that addresses different components in a WBSN.