The neighbor discovery process (NDP) plays a key role in BLE-enabled applications. However, when a massive number of BLE devices are involved in the NDP, signal collisions become severer, which degrade the NDP performance seriously. To solve the problem, BLE 5.0 specifies some extended features such as advanced NDP (ANDP). A-NDP uses more channels and add an auxiliary process to decrease the signal collision rate. The previous works on the performance models for the NDP have focused on the basic NDP (B-NDP). Though some works considered the performance evaluations on A-NDP, they have done on simulations or testbed-based experiments. Likewise, so far, the performance analysis for A-NDP has been insufficient, and the performance optimization scheme is necessary.
Therefore, firstly, we propose an analytical model to evaluate A-NDP performances such as the signal collision probability, the discovery delay, the energy consumption and so on in this dissertation using Chinese Reminder theorem (CRT). With the proposed analysis model, the performances of A-NDP are analyzed from the viewpoint of various operational environments for BLE-enabled IoT services, and compared to those of B-NDP with extended features of Bluetooth 5.0. Besides, it showed that A-NDP is not always better than B-NDP, and we discuss the operational conditions where A-NDP or B-NDP operate effectively, respectively. The simulation results show that the performance of the A-NDP can be improved according the adjustment of BLE parameters.
Secondly, based on the analytical model of A-NDP, we analyze the transmission rate of A-NDP, where the transmission rate is the successful transmission times per second, and propose an optimization model to maximize the transmission rate by adjusting BLE parameters. The simulation results show that the proposed optimization model achieves maximal transmission while maintains lower energy consumption.
At last, we propose an improved A-NDP to overcome the shortage of A-NDP and further improve its performance. In the proposed scheme, we modify the auxiliary process and packet transmission mechanism of the A-NDP, and employs a new parameter, which is used to adjust the signal collision. According the adjustment of this parameter, the optimal performance of the proposed scheme can be achieved.
