Stephanie Sahuguede

Performance and transmission power bound analysis for optical wireless based mobile healthcare applications

In the context of healthcare monitoring, it is necessary to transmit vital information from the patient to an interface managed by the hospital staff. In this work we consider a system where the patient can move within a hospital room and the data collected by sensors are transmitted to a distant receiver placed on the ceiling. We investigate the potentiality of using infrared (IR) communication for the transmission of information in this mobile context. Considering two main IR propagation types (Line Of Sight and diffuse), we characterize the IR mobile channel by using a Gaussian model for the patient location in the room. Thanks to our model, we evaluate the outage probability of this mobile monitoring scheme. From the results, the power efficiency of IR technology to ensure the communication between sensors and the collecting point is established. Moreover, to optimize the system performance and ensure the highest power autonomy, we investigate the possibility of using channel coding. For this purpose, the mobile IR channel outage capacity versus transmission power for different monitoring data rates is calculated. The analysis shows that for a typical data rate of 500 Kbps, it is theoretically possible to optimize the transmission power considering the use of a forward error correction code while maintaining the targeted effective data rate.

LT codes performance over indoor mobile wireless optical channel

In this paper, we consider LOS and diffuse transmission schemes for indoor wireless optical communication taking into account the impact of emitter misalignment and mobility by assuming a realistic scenario (random waypoint). We determine the system performance in terms of outage probability and outage capacity. From the results, we show that the maximum achievable rate is obtained for high outage probabilities. To evaluate the communication rate, we then investigate ARQ and LT (Luby Transform) code performances. Unlike ARQ mechanism, we highlight that LT codes constitute a robust error control mechanism in order to ensure reliable communication when channel conditions degrade. We show that for high outage probability, LOS tracking system complexity can be reduced while conserving identical rate and transmitted power of diffuse configuration can be saved while maintaining significant rate.

Low-density parity-check and fountain code performance over mobile wireless optical channels

By considering error control in different layers, the efficiency of several mechanisms is discussed in the context of wireless optical transmission of mobile health care application data. In this respect, we assume an emitter placed on a monitored patient and a fixed receiver. Because of patient mobility and health care data rate, the wireless optical channel is fading slowly. To ensure reliable communication, we study in the physical layer the low-density parity-check code performance by analysing the results in terms of outage probability. Concerning the application layer, we explore fountain codes, which are also known as Luby transform codes, together with an automatic repeat request mechanism by determining the related outage capacity. Taking into account the performance of both layers, we show that it is possible to design the physical layer code rate in that we maximise the effective data rate in the application layer. Moreover, we point out that Luby transform and low-density parity-check codes constitute an efficient and robust mechanism to reduce optical emitted power, which is of main concern for health care application. Copyright

Performance of a mobile wireless optical CDMA monitoring system

In this paper, we determine the performances of an Optical Code Division Multiple Access (OCDMA) based wireless transmission system for indoor healthcare monitoring application. We consider line of sight communication links between multiple emitters placed on monitored patients and a base station located at the environment ceiling. We first establish an analytical expression of error probability for fixed patient positions, considering On-Off Keying modulation and Optical Orthogonal Codes (OOC). After validation of the theoretical results, we then study the performance degradation because of patient mobility, in terms of outage probability. The impact of mobility is analyzed as a function of patient number, OOC length end environment dimensions. Thanks to our theoretical approach, we show that it is possible to assess the wireless OCDMA system performance for any quality of service.

Transmission Power Analysis of Optical Wireless Based Mobile Healthcare Systems

In the context of healthcare monitoring, it is necessary to transmit vital information from the patient to an interface managed by the hospital staff. In this work we consider a system where the patient can move within a hospital room and the data collected by sensors are transmitted to a distant receiver placed on the ceiling. We investigate the potentiality of using infrared (IR) communication for the transmission of information in this mobile context. Considering two main IR propagation types (line of sight and diffuse), we characterize the IR mobile channel by using a random waypoint mobility for a realistic scenario. Thanks to the mobility model, we evaluate the outage probability of this mobile monitoring scheme. From the results, the power efficiency of IR technology to ensure the communication between sensors and the collecting point is established. Moreover, to minimize the system performance and ensure the highest power autonomy, we investigate the possibility of using channel coding. The analysis shows that for a typical data rate of 500 Kbps, it is theoretically possible to minimize the transmission power considering the use of a forward error correction code while maintaining the targeted information rate.

Performance Bound for LDPC Codes over Mobile LOS Wireless Optical Channel

In this paper we investigate performance of indoor Line of Sight (LOS) Wireless Optical Communication (WOC) considering non stationnarity due to emitter and/or receiver mobility. The transmission scheme uses Low Density Parity Check (LDPC) codes to mitigate performance degradation due to mobility. We evaluate a performance bound for LDPC codes in indoor environment and for a given mobility scenario. We show that this bound directly depends on the Signal to Noise Ratio (SNR) distribution and considering density evolution, on the LDPC code rate. Two methods are developed to evaluate SNR distribution. One is based on Monte Carlo simulations and the other one, on geometrical considerations linked to the room configuration. The obtained results for the performance bound are compared to finite length LDPC code performance.

Adapted LDPC Error Correction Scheme for 2D Optical CDMA Multimedia System

To provide multimedia services in optical networks, 2 dimensional optical code division multiple access (2D OCDMA) system is considered as a potential solution. We focus here on a 2D OCDMA system using 2D multi-weight codes and parallel mapping technique to provide respectively quality of service (QoS) and data rate differentiation. To improve the performance of such a scheme, we investigate forward error correction (FEC) based on low density parity check (LDPC) codes known to have an efficient error correction power for Gaussian channels. We particularly propose an adaptation of the LDPC decoding scheme to the 2D OCDMA multimedia channel which has a specific noise distribution due to multiple access interference (MAI). We evaluate the system robustness to additive white Gaussian noise (AWGN) perturbation in addition to MAI and the gain provided in term of SNR. Finally, we show that the adapted FEC scheme we propose, not only permits improving the data rate per service but also the number of simultaneously communicating users.

Performance of Optical CDMA Systems with Low Density Parity Check Codes

Incoherent optical code division multiple access (OCDMA) is a potential issue for future high speed optical networks. To reduce the number of errors at the detection due in particular to Multiple Access Interference (MAI), we add to the OCDMA link a block of efficient error correction codes named Low Density Parity Check codes (LDPC). The LDPC decoding algorithm, Belief Propagation (BP), usually employed to correct errors due to Gaussian noise, is reconsidered in order to take into account the MAI binomial distribution. The performance of an OCDMA link using 1 Dimensional and 2 Dimensional code sequences along with several LDPC codes is investigated. The performance is enhanced not only in an ideal case with only MAI, but also in a noisy case with MAI and thermal noise. With such error correction coding scheme, the constraints over OCDMA parameters and the signal to noise ratio are greatly relaxed.