Fragility Issues of Medical Video Streaming over 802.11e-WLAN m-health Environments Yow-Yiong Edwin Tan, Nada Philip and Robert S. H. Istepanian Mobile Information and Network Technologies Centre (MINT), Kingston London University Penrhyn Road, Kingston-Upon-Thames, London, KT1 2EE, U. K. Email: edtyy0110@gmail.com Abstract— This paper presents some of the fragility issues of a medical video streaming over 802.11e-WLAN in m-health applications. In particular, we present a Medical Channel- Adaptive Fair Allocation (MCAFA)scheme for enhanced QoS support for IEEE 802.11 (WLAN), as a modification for the standard 802.11e Enhanced Distributed Coordination Function (EDCF) is proposed for enhanced medical data performance. The Medical Channel-Adaptive Fair Allocation (MCAFA) proposed extends the EDCF, by halving the contention window (CW) after ζ consecutive successful transmissions to reduce the collision probability when channel is busy. Simulation results show that MCAFA outperforms EDCF in-terms of overall performance relevant to the requirements of high throughput of medical data and video streaming traffic in 3G/WLAN wireless environments. I. I NTRODUCTION AND MOTIVATION M-Health can be defined as ‘mobile computing, medical sensor, and communications technologies for healthcare’ [1]. This emerging concept represents the evolution of e-health systems from traditional desktop ‘telemedicine’ platforms to wireless and mobile configurations. Current and emerging developments in wireless communications integrated with de- velopments in pervasive and wearable technologies will have a radical impact on future healthcare delivery systems. In this paper, we present an advanced mobile healthcare application example (mobile robotic tele-echography system) that requires a demanding medical data and video streaming traffic in heterogeneous network topology that combines 3G and IEEE 802.11e EDCF QoS WLAN environments. 3G cellular technology is characterised by increased area coverage which is their biggest advantage. On the other hand, 802.11 WLAN, offers high bandwidth connections at low cost but in limited range. These two main stream wireless access methods, have dominant the wireless broadband Internet mar- ket. However the most probable application scenario, is the coexistence of both. Tele-medicine is one of the multimedia application that will benefit from this scenario. The advanced medical robotic system - OTELO (mObile- Tele-Echography using an ultra-Light rObot) was a European IST funded project that develops a fully integrated end-to- end mobile tele-echography system for population groups that are not served locally, either temporarily or permanently, by medical ultrasound experts. It comprises a fully portable tele- operated robot allowing a specialist sonographer to perform a real-time robotised tele-echography to remote patients [2]. OTELO is a remotely controlled system designed to achieve reliable ultrasound imaging at an isolated site, distant from a specialist clinician [3]. Fig 1 shows the main operational blocks. This Tele-echography system is composed of the following: - An “expert” site where the medical expert interacts with a dedicated patented pseudo-haptic fictive probe instrumented to control the positioning of the remote robot and emulates an ultrasound probe that medical experts are used to handle, thus providing a better ergonomy. - The communication media. We developed communication software based upon IP protocol to adapt to different commu- nication (wired and wireless links). - A “patient” site made up of the 6 degrees of freedom (Dof) light weight robotic system and its control unit. Further details on this system are described in [1,2]. With recent advances in mobile technologies, WLAN, PDAs and other hand-held devices featured with different software and hardware capabilities are used by physicians, nurses and other paramedical staff to be updated with the medical reports of patients over the air interface. In this paper, OTELO is integrated in a 3G/WLAN environment so that the health care professional who are on the move, might have continuous access to the patient information. IEEE 802.11e employs a Medium Access Control (MAC), based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The collision avoidance mechanism utilizes the random back-off prior to each frame transmission attempt. It is known that the throughput performance of 802.11e WLAN is significantly compromised as the number of stations increases. As the num- ber of WLAN devices used in OTELO increases, the random nature of the back-off reduces the collision probability, but cannot completely eliminate collisions. This motivates us to propose a new scheme termed Medical Channel-Adaptive Fair Allocation (MCAFA), which combines service differentiation, gentle Contention Window (CW) decrease and an adaptive access scheme. This paper is organized as follows, where, the performance analysis of the expert side medical data of the OTELO system over the WLAN environment is presented (Fig 2). The functional modalities of the OTELO system over the 3G link is presented in Section II. Quality of Service (QoS) over UMTS and WLAN for medical images is investigated in Section III. MCAFA is proposed in Section III. Numerical and simulation results are given and discussed in Section IV. Finally, we draw our conclusions in Section V. Proceedings of the 28th IEEE EMBS Annual International Conference New York City, USA, Aug 30-Sept 3, 2006 SuA09.2 1-4244-0033-3/06/$20.00 ©2006 IEEE. 6316