Rendezvous scheduling in Bluetooth scatternets

Bluetooth scatternets are formed by interconnecting Bluetooth piconets in an ad-hoc fashion and consists typically of the handheld electronic devices from one or more user(s). Thus, scatternets may be used to form and interconnect adhoc Bluetooth personal area networks (PANs). The inter-piconet Bluetooth units, i.e. the gateways interconnecting the piconets in a scatternet, need to time division multiplex their presence in each of their piconets. This requires an interpiconet scheduling (IPS) algorithm, operating in each inter-piconet unit in order to efficiently coordinate its presence with other Bluetooth units. In this paper an IPS algorithm based on periodic rendezvous points is proposed and analyzed with simulations. The algorithm is called Maximum Distance Rendezvous Point (MDRP) and utilizes the Bluetooth SNIFF functionality to establish the periodic rendezvous points between gateways and their peer nodes. The Bluetooth simulator used in the study is based on NS-2, augmented with a scatternet architecture and a Bluetooth MAC layer model. The simulations obtain results regarding TCP behavior and voice delays. The results show that TCP works well with MDRP, but the large round trip delays caused by the inter-piconet gateway nodes give a slowly growing flow control window for TCP. The latter will in particular have impact on the TCP performance in scatternets hosting “thin” (embedded) clients with limited dynamic memory capacity.