Neighbor discovery is the procedure in which two wireless devices initiate a first contact. In low power ad-hoc networks, radios are duty-cycled and the latency until a packet meets a reception phase of another device is determined by a random process. Most research considers slotted protocols, in which the points in time for reception are temporally coupled to beacon transmissions. In contrast, many recent protocols, such as ANT ANT+ and Bluetooth Low Energy (BLE) use a slotless, periodic-interval based scheme for neighbor discovery. Here, one device periodically broadcasts packets, whereas the other device periodically listens to the channel. Both periods are independent from each other and drawn over continuous time. Such protocols provide 3 degrees of freedom (viz., the intervals for advertising and scanning and the duration of each scan phase). Though billions of existing BLE devices rely on these protocols, neither their expected latencies nor beneficial configurations with good latency-duty-cycle relations are known. Parametrizations for the participating devices are usually determined based on a “good guess”. In this paper, we, for the first time, present a mathematical theory which can compute the neighbor discovery latencies for all possible parametrizations. Further, our theory shows that upper bounds on the latency can be guaranteed for all parametrizations, except for a finite number of singularities. Therefore, slotless, periodic interval-based protocols can be used in applications with deterministic latency demands, which have been reserved for slotted protocols until now. Our proposed theory can be used for analyzing the neighbor discovery latencies, for tweaking protocol parameters and for developing new protocols.
@cite_18: Bluetooth Low Energy (BT LE) is a low power air interface technology recently released by the Bluetooth Special Interest Group (BT SIG). As a promising radio, BT LE realizes many designing features to fulfill foreseeable requirements of short range communication, such as fast device discovery, power-saving transmitting, encryption and authentication, etc. In this paper, we focus on the modeling and performance analyzing of the device discovery process in BT LE networks. A general model for device discovery on multi-channel is proposed primarily, which is then tailored and simplified for the BT LE case, where three broadcasting channels are used. Via theoretical analysis, our study reveals that some potential pitfalls are residing in the current version of BT LE specification, i.e. improper parameter settings can significantly deteriorate the device discovery latency and increase meaningless energy consumption. We accordingly propose several strategies seeking ways to tackle the problem. The results of extensive simulation show that our strategies can largely reduce undesirable latency and effectively improve the efficiency of device discovery in BT LE networks.
@cite_26: In this letter, an analytical model is proposed for 3-channel-based neighbor discovery in Bluetooth Low Energy (BLE) networks. The model can be used to determine some important performance metrics, such as average latency or average energy consumption during the course of discovering neighbors. Since intermittent connections are frequently encountered in practical scenarios of BLE, the modeling results can provide a beneficial guidance to customize advertising or scanning behavior towards user desired performance.
@cite_32: 
@cite_17: In wireless sensor networks, energy efficiency is crucial to achieving satisfactory network lifetime. To reduce the energy consumption significantly, a node should turn off its radio most of the time, except when it has to participate in data forwarding. We propose a new technique, called sparse topology and energy management (STEM), which efficiently wakes up nodes from a deep sleep state without the need for an ultra low-power radio. The designer can trade the energy efficiency of this sleep state for the latency associated with waking up the node. In addition, we integrate STEM with approaches that also leverage excess network density. We show that our hybrid wakeup scheme results in energy savings of over two orders of magnitude compared to sensor networks without topology management. Furthermore, the network designer is offered full flexibility in exploiting the energy-latency-density design space by selecting the appropriate parameter settings of our protocol.
In this section, we provide an overview on existing models for periodic interval-based, slotless protocols, such as BLE. As already mentioned, exact models only exist for the trivial case of @math . This implies that the duration of one scan window must be larger than the time between two advertising packets. Therefore, every scan attempt is successful and the discovery latency is limited to roughly @math . The first known model (for @math ) has been presented along with the introduction thew STEM-B protocol @cite_17 , which is one of the first PI-based protocols that have been proposed. In @cite_26 @cite_18 and @cite_32 , this solution has been adopted to the BLE protocol to account for multiple channels, but the limitation to @math remains.