A 2.1µW real-time reconfigurable wearable BAN controller with dual linked list structure

A real-time reconfigurable network controller is proposed for wearable healthcare applications. Based on the dual linked-list structure, it can add or remove the nodes in the network during operation within 8µs and 500ms, respectively. To achieve low power consumption, three schemes of clock gating, low duty-cycled operation, and fixed-order allocation are proposed. As a result, the proposed network controller consumes only 2.1µW in average with 20MHz clock.

I. Introduction

Recently, wearable body area network (BAN) becomes popular for continuous healthcare systems [1] [2] [3]. Usually, the continuous healthcare system consists of several sensors for bio-signal detection, a controller for management, storage, and local processing of the data, and a transceiver for external communication. In this kind of system, the network management is additionally required since it includes not only one node but also several nodes, and this is the role of wearable BAN in the continuous healthcare system. From this manner, the term of “wearable healthcare” is proposed in order to represent the continuous healthcare system based on wearable BAN and sensors. Since the environment is dynamic due to user's movement as shown in Fig. 1(a), wearable healthcare system should be able to compensate it in real time. If there is a sensor deformation during system operation, the measurement result becomes wrong. Fig. 1(b) and (c) shows the change in measurement result between normal and fault case. In wearable healthcare system, it would be the best to detect and compensate the sensor deformation automatically so that users do not need to consider the system status during operation. Therefore, several compensation techniques were adopted especially in the transceivers or sensors in the wearable healthcare systems [4] [5]. But until now, the wearable BAN controllers haven't considered the dynamic environment yet. In this paper, the real-time reconfigurable wearable BAN controller is proposed for several wearable healthcare applications for the first time. It adopts the dual-linked list data structure for easy reconfiguration in both network join and leave case. For network leave case, it can be detected within 500ms in worst case and the leaving sensor is replaced by the back-up sensor. Otherwise, the new sensor can be joined by either join request command for back-up or new connection to the network. It can be performed within 8μs from command transmission, which can be treated as real-time in wearable healthcare system of which data rate is usually less than 10Kbps. Moreover, the proposed controller uses 3 low power schemes of clock gating, fixed order allocation among sensors, and extremely low duty cycled operation in the whole network. Figure 1. Wearable BAN (a) Sensor deformation (fault) during sleep due to user's movement (b) Operation in normal case (c) Operation in fault case