Patent ID: 9547068
Date: 2017-01-17
CPC Classifications: G01S,H04W

Claim:
1. A method at a mobile device, comprising: receiving one or more messages comprising positioning assistance data, said positioning assistance data comprising description of attributes of a plurality of access points (APs), said one or more messages identifying at least two of said plurality of APs as being in a group of APs having similar attributes, wherein said group of APs have an attribute in common comprising an AP model attribute, an AP vendor attribute or an AP LAN chip vendor, or combination thereof; estimating a delay in connection with a round-trip exchange of messages with APs in said group of APs based, at least in part, on measurements obtained from one or more APs in said group of APs, wherein said delay comprises a turnaround calibration factor (TCF) delay or a cyclic shift diversity (CSD) delay or combination thereof and wherein estimating said delay further comprises: measuring a duration of time between transmission of a probe message and receipt of a return message in an exchange of messages with at least one AP in said group of APs; estimating a range to said at least one AP of said group of APs based, at least in part, on an estimated location of said mobile device contemporaneous with said exchange of messages; and estimating said delay based, at least in part, on a comparison of said estimated range to said duration of time; and computing a signal round-trip time (RTT) for at least one AP in said group of APs based, at least in part, on said estimated delay.