A measurement study on 802.11 concurrently used for positioning and communications

Not only the communication capabilities of 802.11, but also the capability to determine the position of mobile devices make 802.11 highly appealing for many application areas. Typically, a mobile device that wants to know its position regularly performs active or passive scans to obtain signal strength measurements of neighboring access points. Active and passive scanning are survey techniques originally intended to be performed once in a while to learn about the presence and signal reception quality of access points within communication range. However, so far, no investigations are known to have been launched into how regular scanning affects concurrent data transmissions from an end-user point of view. In this paper, we explore how common data communication is affected while actively or passively scanning at the same time. We found that with an active scanning interval of equal or greater than 2 seconds the network conditions such as throughput and round trip delay are sufficient for interactive network applications. The use of passive scanning is prohibitive while simultaneously performing interactive data communication due to communication dropouts of more than 1.3 seconds during each scan.