Determination of the Multi-slot Transmission in Bluetooth Systems with the Estimation of the Channel Error Probability
Abstract: Bluetooth is an open specification for a technology to enable short-range wireless communications that operate in an ad-hoc fashion. Bluetooth uses frequency hopping with a slot length of 625 μs. Each slot corresponds to a packet and multi-slot packets of 3 or 5 slots can be transmitted to enhance the trasmission efficiency. However, the use of multi-slot packet may degrade the transmission performance under high channel error probability. Thus, the length of multi-slot should be adjusted according to the current channel condition. Segmentation and Reaseembly (SAR) operation of Bluetooth enables the adjustment of the length of multi-slot. In this paper, we propose an efficient multi-slot transmission scheme that adaptively determines the optimal length of slots of a packet according to the channel error probability. We first discuss the throughput of a Bluetooth connection as a function of the length of a multi-slot and the channel error probility. A decision criteria which gives the optimal length of the multi-slot is presented under the assumption that the channel error probability is known. For the implementation in the real Bluetooth system the channel error probability is estimated with the maximum likelihood estimator (MLE). A simple decision rule for the optimal multi-slot length is developed to maximize the throughput. Simulation experiment shows that the proposed decision rule for the multi-slot transmission effectively provides the maximum throughput under any type of channel error correlation.