Performance evaluation ofaTOA-based trilateration method tolocate terminals in WLAN

time(RTT) measurements between thedevice tobelocated Abstract- Nowadays, several systems areavailable for (inthis casealaptop PC withaWLAN card) andWLAN outdoor localization, suchasGPS,assisted GPS andotheraccess points (APs). Animportant characteristic ofthis system systems working oncellular networks. However, thereisno isitssimplicity (1), asourintention wastouseanexisting properlocation systemforindoorscenarios. Researchinto WLAN infrastructure withminorchanges toprovide an designing location systems for802.11 networks isbeing carried . out, solocating mobile devices onglobal networks (GSM/cellular accurate estimation oftheposition ofthemobile device. The +GPS+WLAN)finally seems feasible. Thetechnique presented system isdivided intotwosubsystems: theranging subsystem inthis paperusesexisting wireless LAN infrastructure with andthepositioning subsystem. Theformer estimates the minorchanges toprovide anaccurate estimation ofthelocation distances between themobile device andtheAPs,andthe ofmobile devices inindoor environments. Thistechnique isbasedlatter calculates thedevice's position usingthedistances on round-trip time(RTT)measurements, whichareusedto estimate distances between thedevice tobelocated andWLAN alreay.estiated.ad.the.Ps'.knwn.postions access points. EachRTT measurement estimates thetimeelapsed between theRTS(Request-to-Send) andtheCTS(Clear-to-Send)