Method and Apparatus for Generating Reference Signals for Accurate Time-Difference of Arrival Estimation

• US 20100260154A1
• Filed: 04/08/2010
• Published: 10/14/2010
• Est. Priority Date: 04/09/2009
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Zhuang, Xiangyang, Love, Robert T., Frank, Colin D., Stewart, Kenneth A., Krishnamurthy, Sandeep H.
• Granted Patent: US 8,730,925 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: G01S 5/0205 Details
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

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.

Claims

1. A method in a wireless terminal, the method comprising:

determining a time location of a subframe based on information signaled from a serving base station or from an identifier associated with a base station, the subframe comprising OFDM symbols over which a transmission corresponds to resource elements arranged on a subcarrier-OFDM symbol grid;

determining whether or not the subframe contains resource elements corresponding to a positioning reference signal based on information signaled from the serving base station or from an identifier associated with the base station; and

receiving the subframe.

2. The method of claim 1,

receiving a positioning reference signal from a first base station;

estimating a time of arrival of the transmission from the first base station relative to a reference clock from the positioning reference signal;

estimating a time of arrival of the 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.

3. The method of claim 1,

receiving a positioning reference signal from a base station on a first set of OFDM symbols wherein transmission resources are arranged as resource element blocks;

generating a 0-1 template matrix such that a number of rows of the template matrix is equal to a number of subcarriers in a resource element block and a number of columns is equal to a number of symbols in the first set of OFDM symbols;

determining a subcarrier location of a positioning reference signal resource element within a resource element block on a symbol as an integer equal to a row index of a non-zero entry on a corresponding column of a submatrix of the template matrix; and

receiving a positioning reference signal from the base station corresponding to transmission on the subcarrier locations.

4. The method of claim 3,

wherein the 0-1 template matrix is a permutation matrix,

wherein a non-zero entry in each column of the template matrix is determined from a mapping function using any one of site identifier of:

the base station;

a physical cell identity of the base station;

a global cell identity of the base station, a system frame number;

a slot number;

a subframe number;

a symbol index;

a resource element block index;

a radio network transaction identity;

or information signaled by the serving base station.

5. The method of claim 3, wherein a 0-1 intermediate matrix is first obtained by cyclically shifting a Costas array of dimension N×

N in one or both dimensions and then inserting K zero rows in-between each group of K consecutive rows of the shifted Costas array and at either a top or bottom of the shifted Costas array such that K>

1 and K is a factor of N, and

the template matrix is set equal to a vertical shift of the intermediate matrix,

an amount of cyclic shift in one or both dimensions of the Costas array and a vertical shift of the intermediate matrix are determined from any one of;

a site identifier of the base station;

a physical cell identity of the base station;

a global cell identity of the base station;

a system frame number;

a slot number;

a subframe number;

a symbol index;

a resource element block index;

a radio network transaction identity;

or information signaled by the serving base station.

6. The method of claim 3,

wherein the 0-1 template matrix is either a cyclically shifted diagonal matrix or a cyclically shifted anti-diagonal matrix,

wherein an amount of cyclic shift is determined from any one of:

a site identifier of the base station;

a physical cell identity of the base station;

a global cell identity of the base station;

a system frame number;

a subframe number;

a resource element block index;

a radio network transaction identity;

or information signaled by the serving base station.

7. The method of claim 3,

wherein the non-zero entry in each column of the 0-1 template matrix is determined from a pseudo-random number generator,

wherein a pseudo-random number generator uses as its input any one of:

a site identifier of the base station;

a physical cell identity of the base station;

a global cell identity of the base station;

a system frame number;

a subframe number;

a resource element block index;

a radio network transaction identity;

or information signaled by the serving base station.

8. The method of claim 3,

wherein the transmission of positioning reference signal resource element corresponds to symbols of a quarternary phase shift constellation generated from a Gold-sequence generator,

wherein an amount a Gold-sequence generator is initialization is determined from any one of:

a site identifier of the base station;

a physical cell identity of the base station;

a global cell identity of the base station;

a system frame number;

a subframe number;

a resource element block index;

a radio network transaction identity;

or information signaled by the serving base station.

9. The method of claim 3,

wherein transmission of positioning reference signal resource elements corresponds to symbols of a cyclically shifted Zadoff-Chu sequence,

wherein a root of the Zadoff-Chu sequence and an amount cyclic shift is determined from any one of:

a site identifier of the base station;

a physical cell identity of the base station;

a global cell identity of the base station;

a system frame number;

a subframe number;

a resource element block index;

a radio network transaction identity;

or information signaled by the serving base station.

10. The method of claim 1,

receiving a 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,

initialization of a pseudo-random number generator is determined from any one of:

a site identifier of the base station;

a physical cell identity of the base station;

a global cell identity of the base station;

a system frame number;

a subframe number;

a resource element block index;

a radio network transaction identity;

or information signaled by the serving base station.

11. The method of claim 3, wherein a 0-1 template matrix is a M×

N matrix whose elements are equal to either a zero (‘

0s’

) or a one (‘

1’

) where M and N are both positive integers.

12. A method in a wireless communication device, the method comprising:

receiving a subframe at the wireless communication device, the subframe including a time dimension and a frequency dimension, the frequency dimension having subcarriers with a center frequency,

the subframe including a plurality of time-frequency resource blocks, a first subset of resource blocks allocated to transmit positioning reference symbols and a second subset of resource blocks allocated for not transmitting the positioning reference signal,

the first subset of resource blocks are disposed nearest the center frequency and the second subset of resource blocks are disposed farther away from the center frequency than the first set of resource blocks,

the subframe including a plurality of positioning reference symbols multiplexed on the first subset of resource blocks;

the wireless communication device de-multiplexing the positioning reference symbols multiplexed on the first subset of resource blocks.

13. The method of claim 12,

the subframe including data multiplexed on the second subset of resource blocks,

the wireless communication device de-multiplexing the data multiplexed on the second subset of resource blocks.

14. The method of claim 12,

the subframe including the cell specific reference symbols (CRS) multiplexed on the first and second subsets of resource blocks,

the wireless communication device de-multiplexing the CRS multiplexed on the first and second subsets of resource blocks.

15. The method of claim 12,

the subframe including the primary and secondary synchronization channels (P/S-SCH) multiplexed on the first subset of resource blocks,

the wireless communication device de-multiplexing the P/S-SCH multiplexed on the first subset of resource blocks.

16. The method of claim 12,

the subframe including the broadcast channel (PBCH) multiplexed on the first subset of resource blocks,

the wireless communication device de-multiplexing the PBCH on the first subset of resource blocks.