## 7 Discussion and Open Research Issues  
The specific technical challenge is to study, analyze and optimize the behavior of energy consumption in a wireless sensor network for medical monitoring. It is necessary to increase efficiency per node, in other words, a greater data transmission per node with respect to a quantity of energy available. It would be relevant to establish different strategies for data transmission over a wireless network with reconfigurable topology. These strategies will use the parameters of the sampling frequency, frequency for sending data, as well as the \"priorities\" of data to send. There are parameters that are more critical than others in a WBSN, therefore the priority in sending data from each sensor is different, e.g., in an emergency situation or critically ill patients. A model of analysis that carry out energy consumption estimations in sensors and personal servers must be considered to create a low energy consumption algorithm for transmission and reception of data with the aim to increase the battery lifetime in a WBSN. Some energy conservation challenges in WBSN must be attained to reach a reliable performance:  
1. _Scheduling_: Design a transmission scheduling for the WBSN in relation to the transfer rate of each vital sign. Characteristics of a model in monitoring and data transmission must be provided. We know that sampling frequency of each sensor, required bandwidth and amount of data are very particular according to the vital sign measured. 2. _Adaptability_: A WBSN must be dynamic and adaptive. Each patient according to his/her condition, shall imply different priorities in terms of the energy consumption, the collection and transmission of data from each sensor. 3. _Communication_: wireless communication is an important factor to evaluate. Each sensor can communicate wirelessly with other sensors or with the base station, however, there are factors that can influence this communication to be successful to optimize energy consumption: 1. Collisions if two sensors try to transmit at the same time (inefficient communication). 2. Retransmissions caused by collisions or loss of information with direct impact on the energy consumption. 3. Mobility of patient: when a patient is moving within different areas in a hospital (Emergency room, laboratory, X-ray, _etc._) data loss or retransmissions could occur if protocol is not designed with mobility support. 4. External factors such as a monitoring environment with heavy traffic information (external devices are transmitting information) or geographic areas that prevent proper communication between network devices. 5. The need to guarantee access to the transmission channel for each sensor according to the priority that involves each of the scenarios for monitoring. 4. _Quality of service_: It is of utmost importance in the monitoring and vital sign transmission; data must be available at the right time, without errors and in real time, so reliability of the network is not affected. 5. _Security:_ The security and privacy of patient-related data are two relevant components for the system security of the WBSN. By data security, it means the protection of information from unauthorized users while data being stored and transferred and data privacy means right of individuals to control the collection and use of personal information. Security and privacy issues are raised automatically when the data is created, transferred, stored and processed. The Health Insurance Portability and Accountability Act (HIPAA) mandates that, as the sensors in WBSN collect the wearer's health data (which is regarded as personal information), care needs to be taken to protect it from unauthorized access and tampering [27]. 6. _Critical time parameters:_ For diagnosis, it is very important that health data (vital signs) of patients arrive within the expected time to accurately indicate the actual health condition of the patient. Delay, packet errors, and packet losses are some factors that could alter the correct medical diagnosis.