Transmitter for transmitting discovery signals, a receiver and methods therein

1. A method, in a base station, for transmitting synchronization signals to a user equipment, wherein the base station and the user equipment are comprised in a radio communications system, the method comprising:

transmitting two or more synchronization signals over two or more directions; and

wherein each synchronization signal is configured to span over a fraction of a carrier bandwidth, the carrier bandwidth is separated into sub-bands, and each of the two or more synchronization signals is configured to span over one sub-band.

2. The method of claim 1 , wherein transmitting the two or more synchronization signals comprises transmitting the two or more synchronization signals in two or more symbols.

3. The method of claim 2 , wherein transmitting the two or more synchronization signals further comprises:

multiplexing, in the frequency-domain, the two or more synchronization signals for the two or more directions; and

transmitting the multiplexed two or more synchronization signals in the two or more symbols.

4. The method of claim 1 , wherein transmitting the two or more synchronization signals further comprises:

multiplexing, in the time-domain, the two or more synchronization signals for the two or more directions; and

transmitting the multiplexed two or more synchronization signals over the same sub-band.

5. The method of claim 1 , wherein transmitting the two or more synchronization signals comprises transmitting the two or more synchronization signals together with information relating to at least one of:

information indicating a beam direction;

information indicating a frequency offset to a carrier center; and

information indicating the base station.

6. The method of claim 1 , wherein transmitting the two or more synchronization signals comprises cyclically, over time, transmitting the two or more synchronization signals into the two or more different directions.

7. A base station for use in a radio communications system, the base station configured to transmit synchronization signals to a user equipment, the base station comprising:

one or more processing circuits operative to control the base station to transmit two or more synchronization signals over two or more directions; and

wherein each of the two or more synchronization signals is configured to span over a fraction of a carrier bandwidth, the carrier bandwidth is separated into sub-bands, and each of the two or more synchronization signals is configured to span over one sub-band.

8. The base station of claim 7 , further operative to:

transmit the two or more synchronization signals in two or more symbols.

9. The base station of claim 8 , further operative to:

multiplex, in the frequency-domain, the two or more synchronization signals for the two or more directions; and

transmit the multiplexed two or more synchronization signals in the two or more symbols.

10. The base station of claim 7 , further operative to:

multiplex, in the time-domain, the two or more synchronization signals for the two or more directions; and

transmit the multiplexed two or more synchronization signals over the same sub-band.

11. The base station of claim 7 , further operative to:

transmit the two or more synchronization signals together with information relating to at least one of:

information indicating a beam direction;

information indicating a frequency offset to a carrier center; and

information indicating the base station.

12. The base station of claim 7 , further operative to:

transmit, cyclically, over time, the two or more synchronization signals into different directions.

13. A method, in a user equipment, for receiving synchronization signals from a base station, wherein the base station and the user equipment are comprised in a radio communications system, the method comprising:

receiving, from the base station, at least a first synchronization signal of two or more synchronization signals that have been transmitted into two or more directions; and

wherein each of the two or more synchronization signals is configured to span over a fraction of a carrier bandwidth, the carrier bandwidth is separated into sub-bands and each of the two or more synchronization signals is configured to span over one sub-band.

14. The method of claim 13 , wherein receiving comprises receiving two or more synchronization signals in two or more symbols.

15. The method of claim 14 , wherein the two or more synchronization signals have been transmitted by:

multiplexing, in the frequency-domain, the two or more synchronization signals for the two or more directions; and

transmitting the multiplexed two or more synchronization signals in the two or more symbols.

16. The method of claim 13 , wherein the two or more synchronization signals have been transmitted by:

multiplexing, in the time-domain, the two or more synchronization signals for the two or more directions; and

transmitting the multiplexed two or more synchronization signals over the same sub-band.

17. The method of claim 13 , wherein receiving comprises receiving at least the first synchronization signal together with information relating to at least one of:

information indicating a beam direction;

information indicating a frequency offset to a carrier center; and

information indicating the base station.

18. The method of claim 13 , wherein the receiving comprises cyclically, over time, receiving the first synchronization signal, which has been transmitted in different directions.

19. A user equipment for use in a radio communications system, the user equipment configured to receive synchronization signals from a base station, the user equipment comprising:

a receiver configured to receive, from the base station, at least a first synchronization signal of two or more synchronization signals that have been transmitted into two or more directions; and

wherein each of the two or more synchronization signals is configured to span over a fraction of a carrier bandwidth, the carrier bandwidth is separated into sub-bands, and each of the two or more synchronization signals is configured to span over one sub-band.

20. The user equipment of claim 19 , further configured to receive the first synchronization signal in two or more symbols.

21. The user equipment of claim 20 , wherein the two or more synchronization signals have been transmitted by:

multiplexing, in the frequency-domain, the two or more synchronization signals for the two or more directions; and

transmitting the multiplexed two or more synchronization signals in the two or more symbols.

22. The user equipment of claim 19 , wherein the two or more synchronization signals have been transmitted by:

multiplexing, in the time-domain, the two or more synchronization signals for the two or more directions; and

transmitting the multiplexed two or more synchronization signals over the same sub-band.

23. The user equipment of claim 19 , wherein the receiver is further configured to:

receive at least the first synchronization signal together with information relating to at least one of:

information indicating a beam direction;

information indicating a frequency offset to a carrier center; and

information indicating the base station.

24. The user equipment of claim 19 , wherein the receiver is further configured to:

receive cyclically, over time, the first synchronization signal, which has been transmitted in different directions.