System and method for generating positioning reference signals

1. A method of transmitting a position reference signal (PRS) to support observed time difference of arrival (OTDOA) position determination in an electronic device, the method carried out by a network node that has a unique identifier and comprising:

a) generating a first PRS sequence;

b) generating a second PRS sequence by modifying the first PRS sequence with a modification function to generate the second PRS sequence, wherein a sum of the first PRS sequence and the second PRS sequence is zero; and

c) transmitting the first and second PRS sequences in a modulated symbol comprising the first and second PRS sequences and the unique identifier of the network node.

2. The method of claim 1 , wherein the first and second PRS sequences are transmitted in respective resource elements of a physical resource block.

3. The method of claim 1 , wherein the first and second PRS sequences are modulated for transmission in an orthogonal frequency divisional multiplexing (OFDM) symbol, wherein the OFDM symbol comprises a first constellation point representing the first PRS sequence and a second constellation point representing the second PRS sequence, the first and the second constellation points rotated 180 degrees from one another and forming a constellation diagram.

4. The method of claim 3 , wherein the constellation point representing the first PRS sequence in the constellation diagram of the OFDM symbol is opposite the constellation point representing the second PRS sequence in the constellation diagram.

5. The method of claim 1 , wherein the network node performs steps b) and c) only upon determining that the electronic device supports generating a first PRS reference sequence and generating a second PRS reference sequence by applying the modification function to the first PRS reference sequence.

6. The method of claim 5 , wherein the determining is carried out using at least one of radio resource control signaling or user equipment capability signaling between the network node and the electronic device.

7. The method of claim 1 , further comprising repeating a) through c) to provide a series of first and second PRS sequences for the electronic device.

8. A radio access node in a radio access network that has a unique identifier, comprising:

a wireless interface configured to conduct communication with an electronic device; and

a control circuit configured to:

a) generate a first position reference signal (PRS) sequence;

b) generate a second PRS sequence by modifying the first PRS sequence with a modification function to generate the second PRS sequence, wherein a sum of the first PRS sequence and the second PRS sequence is zero; and

c) transmit the first and second PRS sequences in a modulated symbol comprising the first and second PRS sequences and the unique identifier of the network node.

9. The radio access node of claim 8 , wherein the first and second PRS sequences are transmitted in respective resource elements of a physical resource block.

10. The radio access node of claim 8 , wherein the first and second PRS sequences are modulated for transmission in an orthogonal frequency divisional multiplexing (OFDM) symbol, wherein the OFDM symbol comprises a first constellation point representing the first PRS sequence and a second constellation point representing the second PRS sequence, the first and the second constellation points rotated 180 degrees from one another and forming a constellation diagram.

11. The radio access node of claim 10 , wherein the constellation point representing the first PRS sequence in the constellation diagram of the OFDM symbol is opposite the constellation point representing the second PRS sequence in the constellation diagram.

12. The radio access node of claim 8 , wherein the control circuit is further configured to perform steps b) and c) only upon making a determination that the electronic device supports generating a first PRS reference sequence and generating a second PRS reference sequence by applying the modification function to the first PRS reference sequence.

13. The radio access node of claim 12 , wherein the determining is carried out using at least one of radio resource control signaling or user equipment capability signaling between the radio access node and the electronic device.

14. The radio access node of claim 8 , wherein the control circuit is configured to repeat a) through c) to provide a series of first and second PRS sequences for the electronic device.

15. A method of conducting observed time difference of arrival (OTDOA) position determination by an electronic device, comprising:

receiving, from a network node with a unique identifier, a first PRS sequence and a second PRS sequence, the second PRS sequence being a modified version of the first PRS sequence by application of a modification function to the first PRS sequence and wherein a sum of the first PRS sequence and the second PRS sequence is zero;

generating a first PRS reference sequence and generating a second PRS reference sequence by applying the modification function implemented by the network node to the first PRS reference sequence;

cross correlating the generated PRS reference sequences and the received PRS sequences; and

determining an estimated time difference of arrival from a result of the cross correlating.

16. The method of claim 15 , wherein the first and second PRS sequences are modulated for transmission by the network node in an orthogonal frequency divisional multiplexing (OFDM) symbol, wherein the OFDM symbol comprises a first constellation point representing the first PRS sequence and a second constellation point representing the second PRS sequence, the first and the second constellation points rotated 180 degrees from one another and forming a constellation diagram.

17. The method of claim 16 , wherein the constellation point representing the first PRS sequence in the constellation diagram of the OFDM symbol is opposite the constellation point representing the second PRS sequence in the constellation diagram.

18. An electronic device that conducts observed time difference of arrival (OTDOA) position determination, comprising:

a wireless interface configured to receive a first PRS sequence and a second PRS sequence from a network node with a unique identifier, the second PRS sequence being a modified version of the first PRS sequence by application of a modification function to the first PRS sequence and wherein a sum of the first PRS sequence and the second PRS sequence is zero; and

a control circuit configured to:

generate a first PRS reference sequence and generate a second PRS reference sequence by applying the modification function implemented by the network node to the first PRS reference sequence;

cross correlate the generated PRS reference sequences and the received PRS sequences; and

determine an estimated time difference of arrival from a result of the cross correlating.

19. The electronic device of claim 18 , wherein the first and second PRS sequences are modulated for transmission by the network node in an orthogonal frequency divisional multiplexing (OFDM) symbol, wherein the OFDM symbol comprises a first constellation point representing the first PRS sequence and a second constellation point representing the second PRS sequence, the first and the second constellation points rotated 180 degrees from one another and forming a constellation diagram.

20. The electronic device of claim 19 , wherein the constellation point representing the first PRS sequence in the constellation diagram of the OFDM symbol is opposite the constellation point representing the second PRS sequence in the constellation diagram.