| IEEE802.11bWi-Fi and Bluetooth are all short-range wireless communication technologies, which have the characteristics of low-power, high-speed, low-cost, short-range, portable link, and so on. In order to be widely used on a global scale, IEEE802.11bWi-Fi and Bluetooth work on the license-free ISM2.4GHz band. However, because of the2.4GHz band Free authorized and openness, that the amount of wireless systems are currently working in the band, such as Bluetooth, Wi-Fi, Wireless USB, ZigBee, cordless phones,microwave ovens and so on, has lead to the band more intensive. The free access of wireless systems in the ISM band must increase the degree of interference between wireless systems, especially for Wi-Fi and Bluetooth, which has been widely used now. The Bluetooth technology developed earlier than Wi-Fi technology. As Wi-Fi defined by IEEE802.11b standard specifies works in the same operating band as Bluetooth, the Bluetooth system is bound to be interfered by the Wi-Fi system. So it is quietly important to research the Bluetooth performance under the interference of the Wi-Fi.This paper first describes the IEEE802.11bWi-Fi two spread spectrum technology on the physical layer, which consisted of direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS),and introduces their technical principles, modulation, data transfer rate. The media access means of distributed coordination function (DCF) and Point Coordination Function (PCF) on MAC layer are compared, and an overview of the CSMA/CA and RTS/CTS protocol are introduced.Secondly, the bottom RF protocol as well as high-level protocol stack, which is consisted of Link Management Protocol LMP, LLC and adaptation protocol (L2CAP), controller interface (Host Controller Interference HCI) protocol, are described in detail.Finally, the overview of the short-range wireless communications interference types and radio channel characteristics and improvement technology are described. Then on the basis of the experimental theory, experimental configuration environment and model, the relationship between the carrier-to-interference ratio C/I, BER, the collision rate, throughput and interference distance d and IEEE802.11bWi-Fi load number can be derived. Last it advised the IEEE802.11b Wi-Fi data load number not only for the minimum collision probability in Bluetooth and Wi-Fi but also for the obtained maximum throughput of Bluetooth. And on this basis the two coexistence mechanism to avoid the interference between Bluetooth and Wi-Fi are given. |
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