Switching between downlink and uplink

1. A method for communications of a time division duplex radio frame provided with at least one special subframe comprising at least one pilot period, the method comprising:

using the at least one special subframe for signalling of all critical control information, and

flexibly allocating other subframes of the radio frame than the at least one special subframe for use as downlink and uplink subframes of the radio frame such that a ratio of time periods for a downlink pilot, a guard period and an uplink pilot of the special subframe is fixed at 6:1:7 or 7:1:6.

2. A method according to claim 1 , comprising transmitting a physical uplink shared channel and/or a physical uplink control channel in an uplink pilot timeslot of the at least one special subframe.

3. A method according to claim 1 , wherein the critical control information comprises at least one of a secondary synchronization signal, a physical broadcast channel, a common reference signal, a channel state information reference signal and radio resource control information.

4. A method according to claim 1 , comprising configuring timing of feedback information and/or grant information associated with a special subframe to coincide with another special subframe.

5. A method according to claim 1 , comprising allocating uplink and/or downlink subframes until a subsequent other special subframe.

6. The method according to claim 1 , wherein the other subframes of the radio frame that are flexibly allocated include subframes of the radio frame that are adjacent to the at least one special subframe.

7. An apparatus comprising:

at least one processor; and

at least one memory including computer program code, the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus to perform at least the following:

to control communications of a time division duplex radio frame provided with at least one special subframe comprising at least one pilot period;

to use the at least one special subframe for signalling of all critical control information; and

to flexibly allocate other subframes of the radio frame than the at least one special subframe for use as downlink and uplink subframes of the radio frame such that a ratio of time periods for a downlink pilot, a guard period and an uplink pilot of the special subframe is fixed at 6:1:7 or 7:1:6.

8. An apparatus according to claim 7 , wherein the special subframe comprises time periods for a downlink pilot, a guard period and an uplink pilot, the apparatus being configured for transmission of a physical uplink shared channel and/or a physical uplink control channel in one of the pilot time periods.

9. An apparatus according to claim 7 , wherein the critical control information comprises at least one of a secondary synchronization signal, a physical broadcast channel, a common reference signal, a channel state information reference signal and a radio resource control information.

10. An apparatus according to claim 7 , configured to time feedback information and/or grant information associated with the special subframe to coincide with another special subframe.

11. An apparatus according to claim 7 , configured to allocate uplink and/or downlink subframes until a subsequent other special subframe.

12. An enhanced Node B or a mobile device comprising the apparatus according to claim 7 .

13. The apparatus according to claim 7 , wherein the other subframes of the radio frame that are flexibly allocated include subframes of the radio frame that are adjacent to the at least one special subframe.

14. A computer program product comprising a non-transitory computer-readable storage medium bearing computer program code embodied therein for use with a computer, the computer Program code comprising code for performing communications of a time division duplex radio frame provided with at least one special subframe comprising at least one pilot period, and comprising:

code for using the at least one special subframe for signalling of all critical control information, and

code for flexibly allocating other subframes of the radio frame than the at least one special subframe for use as downlink and uplink subframes of the radio frame such that a ratio of time periods for a downlink pilot, a guard period and an uplink pilot of the special subframe is fixed at 6:1:7 or 7:1:6.

15. The computer program product according to claim 14 , wherein the other subframes of the radio frame that are flexibly allocated include subframes of the radio frame that are adjacent to the at least one special subframe.