This article provides an introduction to issues of coexistence between Bluetooth and Wi-Fi TM (IEEE 802.11 b), with particular attention to scenarios requiring simultaneous operation, or Sim-OPTM, of both systems in very close proximity. The article explains basic interference mechanisms and quantifies their impact through both actual measurements and simulation. We have developed a detailed simulator that fully models behavior of the PHY and MAC of both Bluetooth and 802.11 b; it is used to expand the analysis and project the mutual impact of collocated Bluetooth and 802.11 b systems across a number of geometries, system parameter settings, and design choices, complementing efforts within the IEEE 802.15.2 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 investigation is that while performance of both systems can degrade when they are collocated, a number of techniques can be employed to virtually eliminate the problems.