| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 93 === Bluetooth is an emerging technology for providing short range, low power, low cost, and ubiquitous wireless environments. In a Bluetooth piconet, the Bluetooth device, known as master, dynamically allocates time slots by way of polling other individual Bluetooth devices called slaves. During the polling interval, a POLL packet will be sent if master has no data to send to the slave; while a NULL packet will be sent if slave has no data to send to the master. Both the POLL and NULL packets are of zero payload and each captures one time slot. In order to avoid transmitting POLL/NULL packets, many polling schemes have been proposed by skipping visit to the slaves that might have no data packet to be sent to the master, but they still have much space to be further improved.
In this thesis, we devise a new, efficient and practicable polling scheme—CRR (Credit-based Round Robin). In this scheme, the visit to each slave is dynamically adjusted based on the current and historical traffic between the master and slave to reduce the visit to idle slaves.
CRR improves the prior polling schemes on four key issues：The first is to enhance the packet transmitting rate and packet receiving rate in a unit time. The second is to avoid unnecessary POLL/NULL packets to save bandwidth and power consumption. The third is to reduce the transmission delay. The fourth is to avoid the starvation and interruption effect.
Our simulation results demonstrate that CRR can enhance the throughput among various numbers of active slaves and idle slaves, can improve the transmitting rate and receiving rate of data packets, can reduce the bandwidth by diminishing the visit to idle slaves, and can decrease the packets end-to-end delay. Moreover, to restrict the number of frames exchanged during a single visit to the slave, a threshold is used to prevent the starvation and interruption effect.
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