| Bluetooth is a wireless communication technology for ad-hoc networks operating at 2.4 GHz ISM (Industrial, Scientific, Medical) band with the initial goal of cable replacement. Now it is used as a communication medium for personal-hand held de vices such as laptops, PDA's, mobile phones, printers etc., thereby forming a Wireless Personal Area Network (WPAN). This results in a large amount of TCP traffic over the Bluetooth Network. The smallest unit of the Bluetooth network is a piconet comprising one master and up to seven active slaves. Larger networks are implemented by interconnection of piconets.; When TCP traffic is carried over a Bluetooth network, complex interactions are expected between congestion control mechanisms and the data link layer. In this research, these interactions were modeled and analyzed in a Bluetooth piconet running TCP new Reno and later the analysis was extended to a scatternet environment (two piconets connected through a bridge). Modeling was implemented using the Artifex simulation tool. The research was performed both in bit error free and error-prone environment. Modeling of the error-prone environment (Bluetooth RF link) was done using a two-state markov channel. The performance metrics TCP goodput, RTT (round-trip time), congestion window size, number of fast retransmits and timeouts were studied in response to a number of data link parameters including buffer size and scheduling algorithms.; The results indicate that in an error free environment satisfactory TCP performance can be obtained by proper dimensioning of the Bluetooth data link parameters. However, in an error-prone environment. TCP performance deteriorates drastically. It was also found that the error-affected packets are mostly retransmitted only by means of timeout.; Keywords. Bluetooth, Piconet, Scatternet, TCP. |
