Method and apparatus for transmitting and/or receiving reference signals

1. An apparatus comprising at least one processor and at least one memory including computer code for one or more programs, the at least one memory and the computer code configured, with the at least one processor, to cause a base station operating in frequency division duplex (FDD) mode at least to:

receive an uplink reference signal from a user equipment using a downlink frequency band which is according to the FDD mode used by the base station to transmit to said user equipment, the base station having according to the FDD mode a different frequency band for receiving from said user equipment, wherein the uplink reference signal is received in a subframe comprising a first portion and a second portion separated by a guard period, wherein the first portion is used for uplink communication and the second portion is used for downlink communication, wherein said uplink reference signal is received in said first portion;

apply prioritization rules to handle collision of the uplink reference signal and other uplink transmission, wherein the other uplink transmission has a priority over the uplink reference signal; and

estimate, using said received uplink reference signal, channel information for the downlink frequency band, without the base station having to first transmit a downlink reference signal on the downlink frequency band.

2. The apparatus of claim 1 , wherein the at least one memory and the computer code, with the at least one processor, are configured to further cause the base station to receive signals from said user equipment on said different frequency band when receiving said uplink reference signal.

3. The apparatus of claim 1 , wherein the at least one memory and the computer code, with the at least one processor, are configured to further cause the base station to configure reference signal resources for the user equipment to transmit the uplink reference signal.

4. The apparatus of claim 1 , wherein the at least one memory and the computer code, with the at least one processor, are configured to further cause the base station to configure a timing of the subframe on the downlink frequency band and comprising the uplink reference signal such that said subframe coincides with a further subframe for at least one user equipment, said further subframe comprising a multi-media broadcast over a single frequency network subframe.

5. The apparatus of claim 1 , wherein the at least one memory and the computer code, with the at least one processor, are configured to further cause the base station to configure a timing of the subframe on the downlink frequency band and comprising the uplink reference signal, wherein configuring the subframe comprises selecting one of a plurality of subframe timing configurations for said subframe having the uplink reference signal.

6. The apparatus of claim 1 , wherein the at least one memory and the computer code, with the at least one processor, are configured to further cause the base station to configure the subframe on the downlink frequency band and carrying the uplink reference signal by selecting one of a plurality of subframe configurations, wherein the plurality of subframe configurations differ in the allocation of symbols between the first portion, the second portion and the guard period.

7. The apparatus of claim 1 , wherein the at least one memory and the computer code, with the at least one processor, are configured to further cause the base station to configure the subframe on the downlink frequency band and carrying the uplink reference signal, wherein configuring the subframe comprises configuring a timing of said subframe such that said subframe coincides with a further subframe for at least one user equipment which does not comprise a random access channel.

8. A method, comprising:

receiving, by a base station operating in frequency division duplex (FDD) mode, an uplink reference signal from a user equipment using a downlink frequency band which is according to the FDD mode used by the base station to transmit to said user equipment, the base station having according to the FDD mode a different frequency band for receiving from said user equipment, wherein the uplink reference signal is received in a subframe comprising a first portion and a second portion separated by a guard period, wherein the first portion is used for uplink communication and the second portion is used for downlink communication, wherein said uplink reference signal is received in said first portion;

applying prioritization rules to handle collision of the uplink reference signal and other uplink transmission, wherein the other uplink transmission has a priority over the uplink reference signal; and

estimating, using said received uplink reference signal, channel information for the downlink frequency band, without the base station having to first transmit a downlink reference signal on the downlink frequency band.

9. The method of claim 8 , further comprising receiving signals from said user equipment on said different frequency band when receiving said uplink reference signal.

10. The method of claim 8 , further comprising configuring reference signal resources for the user equipment to transmit the uplink reference signal.

11. The method of claim 8 , further comprising configuring a timing of the subframe on the downlink frequency band and comprising the uplink reference signal such that said subframe coincides with a further subframe for at least one user equipment, said further subframe comprising a multi-media broadcast over a single frequency network subframe.

12. The method of claim 8 , further comprising configuring a timing of the subframe on the downlink frequency band and comprising the uplink reference signal, wherein configuring the subframe comprises selecting one of a plurality of subframe timing configurations for said subframe having the uplink reference signal.

13. The method of claim 8 , further comprising configuring the subframe on the downlink frequency band and carrying the uplink reference signal by selecting one of a plurality of subframe configurations, wherein the plurality of subframe configurations differ in the allocation of symbols between the first portion, the second portion and the guard period.

14. The method of claim 8 , further comprising configuring the subframe on the downlink frequency band and carrying the uplink reference signal, wherein configuring the subframe comprises configuring a timing of said subframe such that said subframe coincides with a further subframe for at least one user equipment which does not comprise a random access channel.

15. A computer program product embodied on a computer readable medium and comprising computer executable instructions which when run in an apparatus cause a base station operating in frequency division duplex (FDD) mode to perform at least the following:

receiving an uplink reference signal from a user equipment using a downlink frequency band which is according to the FDD mode used by the base station to transmit to said user equipment, the base station having according to the FDD mode a different frequency band for receiving from said user equipment, wherein the uplink reference signal is received in a subframe comprising a first portion and a second portion separated by a guard period, wherein the first portion is used for uplink communication and the second portion is used for downlink communication, wherein said uplink reference signal is received in said first portion;

applying prioritization rules to handle collision of the uplink reference signal and other uplink transmission, wherein the other uplink transmission has a priority over the uplink reference signal; and

estimating, using said received uplink reference signal, channel information for the downlink frequency band, without the base station having to first transmit a downlink reference signal on the downlink frequency band.

16. The computer program product of claim 15 , wherein the computer executable instructions further cause the base station to perform at least the following:

receiving signals from said user equipment on said different frequency band when receiving said uplink reference signal.

17. The computer program product of claim 15 , wherein the computer executable instructions further cause the base station to perform at least the following:

configuring reference signal resources for the user equipment to transmit the uplink reference signal.

18. The computer program product of claim 15 , wherein the computer executable instructions further cause the base station to perform at least the following:

configuring a timing of the subframe on the downlink frequency band and comprising the uplink reference signal such that said subframe coincides with a further subframe for at least one user equipment, said further subframe comprising a multi-media broadcast over a single frequency network subframe.

19. The computer program product of claim 15 , wherein the computer executable instructions further cause the base station to perform at least the following:

configuring a timing of the subframe on the downlink frequency band and comprising the uplink reference signal, wherein configuring the subframe comprises selecting one of a plurality of subframe timing configurations for said subframe having the uplink reference signal.

20. The computer program product of claim 15 , wherein the computer executable instructions further cause the base station to perform at least the following:

configuring the subframe on the downlink frequency band and carrying the uplink reference signal by selecting one of a plurality of subframe configurations, wherein the plurality of subframe configurations differ in the allocation of symbols between the first portion, the second portion and the guard period.