Method and apparatus for generating reference signals for accurate time-difference of arrival estimation
View Patent ↗A base station communicates a positioning reference signal (PRS) to wireless communication devices over a downlink in a wireless communication system by encoding a PRS into a first set of transmission resources, encoding other information into a second set of transmission resources, multiplexing the two sets of resources into a subframe such that the first set of resources is multiplexed into at least a portion of a first set of orthogonal frequency division multiplexed (OFDM) symbols based on an identifier associated with the base station and the second set of resources is multiplexed into a second set of OFDM symbols. Upon receiving the subframe, a wireless communication device determines which set of transmission resources contains the PRS based on the identifier associated with the base station that transmitted the subframe and processes the set of resources containing the PRS to estimate timing (e.g., time of arrival) information.
1. A method in a wireless terminal, the method comprising:
identifying a positioning subframe that may contain a positioning reference signal (“PRS”) transmitted by a first base station based on information signaled from a serving base station, the positioning subframe comprising OFDM symbols over which a transmission corresponds to resource elements arranged on a subcarrier-OFDM symbol grid;
determining whether the identified positioning subframe contains resource elements corresponding to the positioning reference signal based on information signaled from the serving base station;
receiving the identified positioning subframe;
estimating a time of arrival of the received positioning subframe based on the PRS contained in the received positioning subframe; and
receiving the positioning reference signal on a first set of OFDM symbols where the positioning reference signal resource elements are obtained by taking Fast-Fourier Transform of a time-domain sequence obtained from a pseudo-random sequence generator;
wherein initialization of the pseudo-random number generator is determined from any one of: a site identifier of the serving base station, a physical cell identity of the serving base station, a global cell identity of the serving base station, a system frame number, a subframe number, a resource element block index, a radio network transaction identity, and information signaled by the serving base station.
2. The method of claim 1 further comprising:
estimating a time of arrival of the transmission from the first base station relative to a reference dock based on the positioning reference signal;
estimating a time of arrival of a transmission from a second base station;
computing a time difference of arrival of the transmission from the first base station relative to the transmission from the second base station; and
sending a measurement report to the second base station including at least the time-difference of arrival and an identifier associated with the first base station.