Hasso-Plattner-InstitutSDG am HPI
Hasso-Plattner-InstitutDSG am HPI

Controlling Data Transmissions in Public Cellular Networks

In addition to the low population density in the rural areas of Germany, the economic and structural development is often weaker than in urban areas. One such rural region is northern Brandenburg. In 2006, the death rate here after a heart attack was higher than the average rate for all communes in Brandenburg. Moreover, the average rate for the entire Brandenburg region was almost five times higher than that of Berlin, which is a metopolitan area surrounded by Brandenburg. This is one of the reasons why the Fontane project is dedicated to improve medical care of patients with cardiovascular diseases.

An important step in the telemedical care of patients within the Fontane project is the transmission of measured vital signs to a cardiologist. Currently there is a distinction between two levels of urgency. The higher priority is assigned to the data of streaming ECGs, which are transmitted only in emergency situations. The daily recorded vital signs of patients have lower priority.

In order to better cope with the circumstances of the technical and medical environment, this work is based on a prioritization of vital signs according to the health state of the patient. This makes it possible to control data transmission as a function of the available network resources and to consider the frequency with which the doctor evaluates the patient's data. Moreover, the available data transmission rate for the used public cellular network is considered as an important resource. In addition to the end-to-end transmission rate, measurements on the side of the mobile devices also include information from all layers of the protocol stack.

The use of the additional information provides an insight into the flow of communication and helps not only to detect transmission problems, but also take these into account when controlling data transmissions. In this work, a model-based controller was developed which captures data from the different layers of the protocol stack, calculates the available data rate and determines how much of the transmission rate is used by the applications. In certain possible scenarios the same radio network ressources may be shared amongst different mobile devices belonging to different patients. In order to control the data flow for all such devices the location information of the radio network is used - in addition to the approach mentioned above. For this, a control protocol and an algorithm to determine the priority threshold value of the data for each of the used areas in the radio network has been developed.

In order to limit development costs the Fontane project requires the use of standard components, where possible. Therefore, a middleware solution has been selected to implement the control. This middleware platform combines the work of four PhD students. In addition to data transmission, it includes automated analysis of the medical data, integration with existing systems for collecting patient data in hospitals and flexible connectivity of terminals.