Intra-piconet scheduling in Bluetooth

The trend of dynamically interconnecting the personal devices that people carry with them has led to the introduction of personal area networks (PANs) and personal networks (PNs). The Bluetooth wireless access technology is believed to be a potential enabler of PANs and PNs. This dissertation focuses on Bluetooth intra-piconet scheduling (also referred to as Bluetooth polling) that helps in making the Bluetooth technology a successful enabler of PANs and PNs. In order for the Bluetooth technology to be such a successful enabler, its polling mechanism should be efficient. At the same time, the polling mechanism should also be fair. Finally, the polling mechanism must be able to provide quality of service (QoS), which is needed to support audio and video applications. Conventional polling mechanisms are less suitable for Bluetooth as they do not take the Bluetooth specification into account. Current Bluetooth polling mechanisms are either not able to poll in a fair and efficient manner, or they do not provide the needed QoS. In this thesis, a new polling mechanism, named Predictive Fair Poller (PFP), is developed. This polling mechanism predicts the availability of data for each slave, and it keeps track of fairness. Based on these two aspects, it decides which slave to poll next such that the efficiency and fairness are optimized. Further, two new QoS-capable polling mechanisms are developed, namely the fixed-interval poller and the variable-interval poller. These pollers follow the IETF’s Guaranteed Service approach, hence providing both a rate guarantee and a delay guarantee. With respect to Bluetooth polling, this is new. The fixed-interval poller plans polls to slaves with fixed intervals, whereas the variable-interval poller postpones polls for slaves, whenever possible, in order to save bandwidth. The fixed-interval poller and the variable-interval poller provide, with some predefined maximum deviation, a rate guarantee, which leads to a delay guarantee, provided that the traffic sources comply to their traffic flow specification. These two types of guarantees are the main QoS types that are needed for audio and video applications. Additionally, retransmission strategies are developed that minimize the influence of bad radio environments on the provisioning of these QoS types. The mechanisms and techniques developed in this work are evaluated by means of simulation studies. These studies show that PFP is fair and efficient. In particular, the studies show that PFP performs at least as good as and sometimes better than existing Bluetooth polling mechanisms. Furthermore, the studies show that the variable-interval poller outperforms the fixed-interval poller, and that it is able to guarantee delay bounds that approach the delay bounds that can be guaranteed using a synchronous connection-oriented (SCO) channel. Moreover, the variable-interval poller is able to do so while consuming less resources. As the variable-interval poller can also perform retransmissions, this saved bandwidth can be used to avoid the link quality problems of SCO channels in bad radio environments, while keeping up QoS.