Method and arrangement for positioning in a wireless communications system

1. A method comprising:

determining, based on an output of a function, whether a type of the positioning subframe to transmit is to be a measurement subframe or a low-interference subframe, wherein the measurement subframe includes at least one symbol occupying a time-frequency resource on which a user equipment detects the at least one symbol; and

transmitting the determined type of positioning subframe, wherein the determining comprises:

comparing the output of the function with a threshold value, wherein the output of the function is determined based on a pseudo-random sequence and network cell information, the pseudo-random sequence is determined by the following:

c ( n )=( x 1 ( n+N c )+ x 2 ( n+N c ))mod 2,

 and the threshold value is associated with a probability that the type of the positioning subframe is a low-interference subframe;

in response to the output of the function being different from the threshold value, determining that the type of the positioning subframe is a measurement subframe; and

in response to the output of the function matching the threshold value, determining that the type of the positioning subframe is a low-interference subframe.

2. The method of claim 1 , wherein the threshold value is common to each cell in the wireless communication network for determining the type of positioning subframe to transmit in that cell.

3. The method of claim 1 , further comprising transmitting the threshold value to a user equipment configured to perform positioning measurements on positioning subframes.

4. The method of claim 1 , wherein the user equipment performs positioning measurements on the at least one symbol.

5. The method of claim 1 , wherein a low-interference subframe is transmitted in a cell on a frequency resource and contributes no more than minimal interference to measurement subframes transmitted by neighboring cells on that same frequency resource.

6. The method of claim 1 , wherein the transmitting comprises transmitting the determined type of positioning subframe in a cell of the wireless communication network.

7. The method of claim 1 , wherein a subframe has one or more parts within which data scheduled for transmission during that subframe is to be included, the data distinguished from control signaling, and wherein a low-interference subframe is a subframe which has less than a maximum possible amount of data scheduled within the one or more parts.

8. A network node configured to transmit a positioning subframe in a wireless communication network, comprising:

a processor configured to:

determine, based on an output of a function, whether a type of the positioning subframe to transmit is to be a measurement subframe or a low-interference subframe, wherein the measurement subframe includes at least one symbol occupying a time-frequency resource on which a user equipment detects the at least one symbol;

compare the output of the function with a threshold value, wherein the output of the function is determined based on a pseudo-random sequence and network cell information, the pseudo-random sequence is determined by the following:

c ( n )=( x 1 ( n+N c )+ x 2 ( n+N c ))mod 2,

 and the threshold value is associated with a probability that the type of the positioning subframe is a low-interference subframe;

in response to the output of the function being different from the threshold value, determine that the type of the positioning subframe is a measurement subframe; and

in response to the output of the function matching the threshold value, determine that the type of the positioning subframe is a low-interference subframe; and

a subframe transmitting unit configured to transmit the determined type of positioning subframe.

9. The network node of claim 8 , wherein the subframe transmitting unit is configured to transmit the determined type of positioning subframe in a cell of the network, wherein the network node further comprises a cell identifier obtaining unit configured to obtain a cell identifier for the cell, wherein the at least one parameter includes the cell identifier, and wherein the processor is configured to determine the type of the positioning subframe to transmit in said cell based upon a comparison.

10. The network node of claim 8 , wherein the threshold value is common to each cell in the wireless communication network for determining the type of positioning subframe to transmit in that cell.

11. The network node of claim 8 , wherein the subframe transmitting unit is further configured to transmit the threshold value to a user equipment configured to perform positioning measurements on positioning subframes.

12. The network node of claim 8 , wherein the user equipment performs positioning measurements on the at least one symbol.

13. The network node of claim 8 , wherein a low-interference subframe is transmitted in a cell on a frequency resource and contributes no more than minimal interference to measurement subframes transmitted by neighboring cells on that same frequency resource.

14. The network node of claim 8 , wherein the node is an evolved NodeB.

15. The network node of claim 8 , wherein the subframe transmitting unit is configured to transmit the determined type of positioning subframe in a cell of the wireless communication network.

16. The network node of claim 8 , wherein a subframe has one or more parts within which data scheduled for transmission during that subframe is to be included, the data distinguished from control signaling, and wherein a low-interference subframe is a subframe which has less than a maximum possible amount of data scheduled within the one or more parts.

17. The method of claim 1 , wherein the low-interference subframe comprises at least one reference symbol.

18. The network node of claim 8 , wherein the low-interference subframe comprises at least one reference symbol.

19. The network node of claim 8 , wherein the node is a user equipment.