I. Introduction
Bluetooth Low Energy (BLE) is a wireless personal area network technology aimed at smart applications in the healthcare, fitness, beacons, home entertainment, etc [1] . Compared to Bluetooth Classic, BLE technology is intended to significantly reduce power consumption at considerably lower cost. From version 4.2 the BLE specification includes IPv6 connectivity implemented as the Internet Protocol Support Profile (IPSP), which uses a Bluetooth-optimized version of 6LoWPAN [2] . The addition of 6LoWPAN means that each BLE device can be accessed globally and the number of addresses available for the Internet of Things (IoT) will be all but inexhaustible [3] , [4] . However, this 6LoWPAN over BLE approach also comes with some downsides as follows. Increased memory space is necessary to generate and process relatively large IPv6 packets. Because the IP encapsulation and decapsulation are done over IPSP, the processing and computation overhead can be increased. In addition, the BLE device needs to have a heavier network stack. As a result, the BLE devices suffer from larger power consumption. Further-more, IP-based protocols are not supported in early versions of BLE and many typical Bluetooth devices are not connected to the Internet. Due to the limitations, the 6LoWPAN over BLE approach is not always the best choice for constrained nodes.