Wireless Optical Technology Based Body Area Network for Health Monitoring Application MUHAMMAD REZA RAFLY SIDIQ A GEDE TEGUH

Application Layer  An application layer is an abstraction layer that specifies the shared protocols and interface methods used by hosts in a communications network. The application layerabstraction is used in both of the standard models of computer networking; the Internet Protocol Suite (TCP/IP) and the Open Systems Interconnection model (OSI model).

Introduction  Wireless Optical Communication (WOC) technology is now established as an alternative or complement to radiofrequency in particular for indoor transmissions. Besides, considering the crucial issue of the electromagnetic pollution in a sensible environment such as hospital, WOC is a good candidate for medical applications, such as Wireless Body Area Network (WBAN) dedicated to health monitoring.

 They investigate the feasibility of an optical WBAN, exploiting diffuse optical reflections over the patient environment, and using spreading codes to realize network on-body nodes multiple access. Considering optical WBAN nodes distributed on the patient body, a theoretical analysis has been developed to evaluate the error probability distribution. Assuming perfect blocking because of the body regarding optical beams, the study takes into account the BAN mobility in terms of node orientation and patient location. A typical health monitoring scenario has been considered as an example, and the achievable performance of the wireless optical solution is reported and discussed regarding medical requirements.

Medical WBAN Scenario  These three sensors are integrated into wireless optical communicating nodes and constitute a WBAN assuming that the BAN coordinator is also worn by the person. Usually, the most performing way to achieve a wireless optical link is to consider a Line of Sight (LOS) scheme. However, establishing a direct optical link considering case (a) is difficult regarding the variety of human body morphologies and body movements.

 They avoid complex alignment devices considering NLOS propagation based on diffuse reflections. So, Each emitting node is considered to be an ideal Lambertian Infrared (IR) optical source.  The optical receiver is composed of a photo-detector with a large Field of View (FOV) of 70 degrees and a physical surface of 1cm². To simplify the analysis, They using no obstacle such as beds or monitoring machines is present in the room. However, the body of the patient is supposed to be a blocking surface for optical beams in our setup.

Theoritical  Data are sent using Intensity Modulation and Direct Detection (IM/DD). The received signal thus depends on the incident optical power and the photo-detector responsivity  Considering a star WBAN topology, we investigate OCDMA scheme based on the assignment of a specific code to each BAN node to perform multi-user communications. Regarding indoor wireless IR channels, this technique has been shown to be a well suited method because of its flexibility and ease of implementation  Moreover, each emitting node is supposed to transmit independent and equiprobable binary data, using an On/Off Keying (OOK) modulation. Each node is identified by a unipolar Optical Orthogonal Code (OOC) sequence of length F, and weight W with maximal cross- correlation and auto-correlation equal to 1

Conclusion  The use of diffuse WOC in order to develop medical mobile WBAN. A typical health monitoring setup composed of three nodes and a coordinator has been considered as an example to evaluate optical WBAN feasibility. Optical beam blocking because of patient body and WBAN mobility in terms of node orientation and patient location in an empty room have been taken into account for the channel modeling. This model has been used to determine the theoretical performance of the WBAN scenario, regarding a CDMA multiple access scheme using OCCs and HL receiver. For this purpose, we have established and validated by simulation an analytical expression of the error probability for such a WBAN.

 They determined the performance of diffuse WOC for WBAN, in terms of data rate, power consumption and flexibility, using as a criterion the blocking probability of the transmitted data. These results must be optimized by considering a more realistic environment for the channel modeling, which would include equipments and furnitures in order to evaluate the impact of blocking effects. In addition, these results remain to be confirmed with practical experiments.

References  Wireless Optical technology based Body Area Network for Health Monitoring Application  L. Chevalier, S. Sahuguède, Member, IEEE, and A. Julien-Vergonjanne, Member, IEEE. University of Limoges, XLIM UMR 7252/Labex Sigma-Lim, France