Enhanced Channel Access for Connection State of Bluetooth Low Energy Networks

According to Bluetooth Low Energy (BLE) specifications, a pair of connected devices (master and slave) should sleep whenever packet transmission is failed twice consecutively, although they still have packets to be sent. However, when BLE devices are densely deployed in a small geographical area, such sleeping can occur frequently, and as a result, the BLE performance can be degraded largely. Moreover, when considering that a message consists of multiple packets in many Internet of things (IoT) applications, the situation gets worse because the master and slave of BLE alternately have the transmission opportunity not in the unit of message but in the unit of packet. In this paper, we suggest two enhancements of data channel access for improving the BLE performance by making up the above-mentioned weaknesses: One is to continue packet transmission by avoiding bad-quality channel via channel hopping instead of sleeping; the other is a message-based alternation of transmission opportunity between master and slave. We formulate a Markov model for analyzing the performance of the proposed scheme and derive a closed-form solution. The numerical results demonstrate that, from the proposed two enhancements, the throughput and delay performances of BLE are remarkably improved with a slight increase of consumed energy.