LTE Positioning Reference Signals (PRS)

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Positioning reference signals are used for OTDOA User Plane Location Support. Positioning reference signals are transmitted with a periodicity Tprs[ms], as specified by prsPeriod. At each transmission occasion the position reference signals are sent in n,subf,con consecutive DL subframes. The number of consecutive DL subframes can be specified by nConsecutiveSubframes. In the figure below an example of the transmission scheme for PRS subframes is shown. 


To minimize the interference in the PRS subframes PDSCH is not scheduled in any RB in those subframes. Also note that PBCH, PSS and SSS all have higher priority than PRS. For a configuration with two antennas, PRS is transmitted from one antenna at the time. The same antenna is used the entire PRS occasion. For more information, refer to OTDOA User Plane Location Support. The more PRS subframes, the more accurate will the OTDOA positioning be. This comes at the expense of less resource available for PDSCH. The fraction of subframes used for PRS can be calculated by the following formula:

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