Huan Bang Li

R&D and standardization of body area network (BAN) for medical healthcare

A new major application of UWB is medical healthcare using advantages of low power spectrum density, high capacity of transmission and accurate ranging. As a core network of medical healthcare based on ICT, i.e. medical ICT, a body area network (BAN) has been researched and developed. BAN can provide a wide range of applications in primary for medical healthcare such as tele-metering vital sign, e.g. ECG, EEG, tele-controlling medical equipment, e.g. capsule endoscope and in addition for non-medical service such as entertainment. To harmonize with the strong demands from both medical healthcare societies and ICT industries, a standardization committee referred to as IEEE 802.15.6 was formally set up in December 2007. The objective of 15.6 is to define new physical (PHY) and media access control (MAC) layers for wireless BAN (WBAN). This invited paper introduces a progress of research and development of body area network, i.e. BAN and its standardization in IEEE802.15.6 in a field of medical ICT in order to encourage global collaboration as well as planting many R&D and business seeds in academia and industry.

IEEE body area networks and medical implant communications

IEEE 802.15 established a new working group, wireless body area networks (WBAN), to develop short range wireless technology in and around human body recently. This paper investigates networking issues in implant communications of WBAN. The object is better understanding of medical implant sensor networks and how to start WBANs work. We applied IEEE 802.15.4b and 802.15.4a-chirp spread spectrum (CSS) for implant communications. We found two issues: clear channel assessment of implant devices and adjacent-channel interference from free space signals. Both of them can be attributed to the rapid attenuation of electromagnetic wave through tissues. Therefore the carrier sense multiple access mechanism and transmit mask of 802.15.4b cannot be directly adopted. The modulation of 802.15.4a-CSS is a good reference to WBAN. Besides, a simple two-hop protocol which uses a body surface forwarder was presented for long distance wireless implant communications.

IEEE Body Area Networks for Medical Applications

IEEE 802.15 working group established a new study group, body area network (SG-BAN), to develop short range wireless communication technology in and around human body recently. Wearable healthcare is an important category of potential applications of BAN. This paper introduces the IEEE SG-BAN and investigates the performance of 802.15.4b and 802.15.4a for wearable healthcare applications in the heterogeneous networks environment. The object is better understanding of healthcare requirement of BAN and how and where BAN works to be started. In addition to the scalability issue, we found asymmetric clear channel assessment (CCA) abilities among different types of wireless technology. The asymmetric CCA has significant impact on system performance.

Introduction of SG-BAN in IEEE 802.15 With Related Discussion

Body area networks (BAN) can provide a wide range of applications including medical support, healthcare monitoring, and consumer electronics with increased convenience or comfort. To harmonize with the strong demands from both medical and healthcare societies and ICT industries, a study group referred to as IEEE 802.15.BAN (SG-BAN) was formally set up in November 2006. The objective of SG-BAN is to define project authorization request (PAR) and five criteria (5C) and to lead the group up to the next standardization step. This paper presents a general guidance of SG-BAN. The main up-to-data activities in SG-BAN are introduced. Current status and main issues are overviewed. Some critical and future works are suggested.

Channel model on various frequency bands for wearable Body Area Network

Body Area Network (BAN) is considered as a promising technology in supporting medical and healthcare services by combining with various biological sensors. In this paper, we look at wearable BAN, which provides communication links among sensors on body surface. In order to design a BAN that manages biologic information with high efficiency and high reliability, the propagation characteristics of BAN must be thoroughly investigated. As a preliminary effort, we measured the propagation characteristics of BAN at frequency bands of 400 MHz, 600 MHz, 900 MHz, and 2400 MHz respectively. Channel models for wearable BAN based on the measurement results were derived. Our results show that the channel models can be described by using a path loss model for all investigated frequency bands.

Hybrid Unified-Slot Access Protocol for Wireless Body Area Networks

Wireless body area network (WBAN) solution is an emerging new technology to resolve the small area connection issues around human body, especially for the medical applications. Based on the integrated superframe structure of IEEE 802.15.4, a modified medium access control (MAC) protocol, named Hybrid Unified-slot Access (HUA) protocol for WBANs is proposed with focus on the simplicity, dependability and power efficiency. Considering the support to multiple physical layer (PHY) technologies including ultra-wide band (UWB), the slotted ALOHA is employed in the contention access period (CAP) to request the slot allocation. Mini-slot method is designed to enhance the efficiency of the contention. Moreover, sufficient slot allocation in the contention-free period (CFP) makes HUA adaptive to the different traffic including the medical and non-medical applications. Simulation results show that the protocol effectively decreases the probability of collision in a CAP and extends the CFP slots to support more traffic with quality of service (QoS) guarantee.

Clock Offset Compensation in Ultra-Wideband Ranging

Accurate and low-cost sensor localization is critical for deployment of wireless sensor networks. Distance between Ultra-wideband (UWB) sensor nodes can be obtained by measuring round trip flying time through two-way ranging (TWR) transaction. Because of difficulties in synchronization and channel estimate, the response delay of UWB node is the order of milliseconds. Comparing with the nanosecond propagation delay, relative clock offset between UWB nodes introduces big error in TWR. This paper presents the management of relative clock offset in TWR transaction. The relative clock offset between sensors is estimated by comparing the claimed and real frame duration. Simulation in the UWB channel model shows the relative clock offset after compensation can be reduced to less than ±2 ppm.

Scalable and robust medium access control protocol in wireless body area networks

Wireless body area network (WBAN) solution is an emerging technology to resolve the small area connection issues around human body, especially for the medical applications. Based on the integrated superframe structure of IEEE 802.15.4, this paper proposes a modified medium access control (MAC) protocol for WBAN with focus on the simplicity, dependability and power efficiency. Considering the support to multiple physical layer (PHY) technologies including ultra-wide band (UWB), the slotted ALOHA is employed in the contention access period (CAP) to request the slot allocation. Mini-slot method is designed to enhance the efficiency of the contention. Moreover, sufficient slot allocation in the contention-free period (CFP) makes the proposed protocol adaptive to the different traffic including the medical and non-medical applications. Simulation results show that the protocol effectively decreases the probability of collision in a CAP and extends the CFP slots to support more traffic with quality of service (QoS) guarantee.

Wireless Body Area Network Combined with Satellite Communication for Remote Medical and Healthcare Applications

Wireless Body Area Network (WBAN) is expected to play an important role in supporting medical and healthcare services with increased convenience and comfort. One main advantage of WBAN is that it enables automatic biosignal collection in real time which is essential in medical treatment and healthcare vigilance. To harmonize with the strong demands from both medical and healthcare societies, and information and communications technology industries, IEEE 802 Standard Committee set up a task group of TG15.6 to develop an IEEE wireless standard on WBAN. In this paper, we first review the main activities of TG15.6 with the updated status. Then, we present a prototype WBAN system that is implemented by using ultra-wideband technology. Multi-hop mechanism is adopted to guarantee reliable connection. Finally, we describe an experimental system that uses the developed WBAN system by combining with satellite communication in supporting remote medical treatment and healthcare. In case of less of medical resources such as in emergency, in rural or isolated areas, such a system is important in sending the corresponding biosignal to a remote hospital in real time to help patient management. The relative delay of WBAN data delivery via satellite is measured which is dependent on the satellite link capacity.

Clock management in Ultra-wideband Ranging

The distance between two asynchronous impulse ultra-wideband (UWB) sensors can be obtained from round trip flying time through two-way ranging (TWR) transaction. The clock difference causes error in the flying time measurement account for the order of 10 nanoseconds propagation delay. This paper presents a clock management between UWB sensors in the TWR transaction. The ranging responder estimates the clock of ranging initiator by a delay-locked-loop circuit during reception of ranging frame. When replying the response, the ranging responder locks its clock frequency to the estimated clock of ranging initiator. Consequently the duration of TWR are measured by the same clock. The simulation over the UWB channel models results shows that the relative clock offset can be reduced to less than plusmn1.2 ppm in the worst channel mode.