Wi-Fi (802. 11 b) and bluetooth: enabling coexistence - IEEE Network

This article provides an introduction to issues of coexistence between Bluetooth and WiFiTM (IEEE 802.1 1 b), with particular attention toscenarios requiring simultaneousoperation, or Sim-OPTM, of both s stems in very close proximiiy. The article explains basic interference mechanisms an cy quantifies their impact through both actual measurements and simulation. W e have developed a detailed simulator that fully models behavior of the PHY and MAC of both Bluetooth and 802.1 1 b; it is used to expand the analysis and roject the mutual impact of collocated Bluetooth and 802.1 1 b systems across a numEer of geometries, system parameter settings, and design choices, complementing efforts within the IEEE 802.1 5.2 Task Group, which are also discussed. The article concludes with a discussion of techniques with the potential to greatly improve the performance of collocated Bluetooth and Wi-Fi systems. A key result of this investi ation i s that while performance of both systems can degrade when they are collocate$ a number of techniques can be employed to virtually eliminate the problems. he 2.4 GHz industrial, scientific, and medical (ISM) band is poised for strong growth. Fueling this growth are two emerging wireless technologies: wireless personal area networking (WPAN) and wireless local area networking (WLAN). The WPAN category is led by a shortrange wireless technology called Bluetooth. Designed principally for cable replacement applications, most Bluetooth implementations support a range of up to roughly 10 m, and speeds of up to 700 kb/s for data or isochronous voice transmission. Bluetooth is ideal for applications such as wireless headsets, wireless synchronization of personal digital assistants (PDAs) with computers, and wireless peripherals such as printers or keyboards. Cahners In-Stat predicts the market for Bluetooth devices will reach 800 million units by 2004 [l]. The WLAN category has several technologies competing for dominance; however, based on current market momentum, it appears that Wi-Fi (IEEE 802.11b)' will prevail. Wi-Fi offers speeds of 11 Mb/s and covers a range of up to 100 m. With WLANs, applications such as Internet access, e-mail, and file sharing can now be done in the home or office with new levels of freedom and flexibility. Cahners predicts WLAN shipments of more than 5 million units in 2004, implying an installed base of nearly 20 million systems [2].2 WPAN and WLAN are complementary rather than competing technologies. Moreover, with both of them expecting rapid growth, collocation of Bluetooth and Wi-Fi devices will become increasingly likely, especially in computing devices. While there are certainly many devices where different radio technologies can be built into the same platform (e.g., Bluetooth in a cellular phone), collocation of Wi-Fi and Bluetooth 1 In this article the terms 802.11b and Wi-Fi will be used interchangeably. The mark Wi-Fi belongs to the Wireless Ethernet Compatibility Alliance, and the Bluetooth mark belongs to the Bluetooth SIC, Inc. The term SimOP is trademarked by Mobilian Corporation; other signs and marks used in this article are the p r o p e e of their respective owners. is of special significance because both occupy the 2.4 GHz frequency band. This creates the potential for interference between the two technologies, and hence the need for coexistence. In this article we will use the term coexistence to mean wireless systems can be collocated without significantly impacting the performance of either [3]. In recognition of the need for coexistence between these (and other) systems, the IEEE (who developed the 802.11b specification on which Wi-Fi is based) has created a coexistence task group, IEEE P802.15.2; and the Bluetooth SIG has created a Coexistence Working Group. The outcome of the work of these groups will be a set of recommended practices for the industry. Much of the work presented in this article either contributed directly to the efforts of these groups or complemented them.