Methods and apparatus for flexible use of frequency bands

1. A method for a mobile device in an orthogonal frequency division multiplex (OFDM) communication system that utilizes two or more carriers for communication with a plurality of mobile devices, the method comprising:

receiving broadcast information indicating a plurality of carriers for communication;

receiving a first signal via a first downlink (DL) carrier of the plurality of carriers and a second signal simultaneously via a second DL carrier of the plurality of carriers, wherein the first DL carrier has a wider bandwidth than the second DL carrier and the first signal received via the first DL carrier has an increased subcarrier spacing in frequency and shorter OFDM symbols in time than the second signal received via the second DL carrier, wherein the first DL carrier is a different carrier than the second DL carrier; and

transmitting a signal via a third uplink (UL) carrier of the plurality of carriers.

2. The method of claim 1 , further comprising receiving a message including system information via the second DL carrier, the message indicating that the third UL carrier is paired to the second DL carrier.

3. The method of claim 1 , wherein the first DL carrier is a time division duplex (TDD) carrier and the third UL carrier is a same frequency carrier as the first DL carrier.

4. The method of claim 1 , further comprising performing cell search by scanning frequency bands to periodically receive synchronization signals to acquire time and frequency synchronization for the second DL carrier and to detect a cell identity associated with the second DL carrier.

5. The method of claim 1 , wherein the second DL carrier is a primary DL carrier and the first DL carrier is an auxiliary DL carrier.

6. The method of claim 1 , wherein the UL carrier is at a higher frequency than the second DL carrier, wherein the second signal is spatial multiplexed, and wherein the signal transmitted via the third UL carrier is beamformed.

7. The method of claim 1 , wherein the first DL carrier is in an unlicensed band and the third UL carrier is in a licensed band, and wherein the unlicensed band is only used by the OFDM communication system for downlink communication.

8. A mobile device in an orthogonal frequency division multiplex (OFDM) communication system that utilizes two or more carriers for communication with a plurality of mobile devices, the mobile device comprising:

a receiver configured to:

receive broadcast information indicating a plurality of carriers for communication; and

receive a first signal via a first downlink (DL) carrier of the plurality of carriers and a second signal simultaneously via a second DL carrier of the plurality of carriers, wherein the first DL carrier has a wider bandwidth than the second DL carrier and the first signal received via the first DL carrier has an increased subcarrier spacing in frequency and shorter OFDM symbols in time than the second signal received via the second DL carrier, wherein the first DL carrier is a different carrier than the second DL carrier; and

a transmitter configured to transmit a signal via a third uplink (UL) carrier of the plurality of carriers.

9. The mobile device of claim 8 , wherein the receiver is further configured to receive a message including system information via the second DL carrier, the message indicating that the third UL carrier is paired to the second DL carrier.

10. The mobile device of claim 8 , wherein the first DL carrier is a time division duplex (TDD) carrier and the third UL carrier is a same frequency carrier as the first DL carrier.

11. The mobile device of claim 8 , wherein the receiver is further configured to perform cell search by scanning frequency bands to periodically receive synchronization signals to acquire time and frequency synchronization for the second DL carrier and to detect a cell identity associated with the second DL carrier.

12. The mobile device of claim 8 , wherein the second DL carrier is a primary DL carrier and the first DL carrier is an auxiliary DL carrier.

13. The mobile device of claim 8 , wherein the UL carrier is at a higher frequency than the second DL carrier, wherein the second signal is spatial multiplexed, and wherein the signal transmitted via the third UL carrier is beamformed.

14. The mobile device of claim 8 , wherein the first DL carrier is in an unlicensed band and the third UL carrier is in a licensed band, and wherein the unlicensed band is only used by the OFDM communication system for downlink communication.

15. A method for a base station in an orthogonal frequency division multiplex (OFDM) communication system that utilizes two or more carriers for communication with a plurality of mobile devices, the method comprising:

transmitting broadcast information indicating a plurality of carriers for communication;

transmitting, to a mobile device, a first signal via a first downlink (DL) carrier of the plurality of carriers and a second signal simultaneously via a second DL carrier of the plurality of carriers, wherein the first DL carrier has a wider bandwidth than the second DL carrier and the first signal received via the first DL carrier has an increased subcarrier spacing in frequency and shorter OFDM symbols in time than the second signal received via the second DL carrier, wherein the first DL carrier is a different carrier than the second DL carrier; and

receiving, from the mobile device, a signal via a third uplink (UL) carrier of the plurality of carriers.

16. The method of claim 15 , further comprising transmitting a message including system information via the second DL carrier, the message indicating that the third UL carrier is paired to the second DL carrier.

17. The method of claim 15 , wherein the first DL carrier is a time division duplex (TDD) carrier and the third UL carrier is a same frequency carrier as the first DL carrier.

18. The method of claim 15 , further comprising:

periodically transmitting synchronization signals used for time and frequency synchronization for the second DL carrier; and

transmitting an indication of a cell identity associated with the second DL carrier.

19. The method of claim 15 , wherein the second DL carrier is a primary DL carrier and the first DL carrier is an auxiliary DL carrier.

20. The method of claim 15 , wherein the UL carrier is at a higher frequency than the second DL carrier, wherein the second signal is spatial multiplexed, and wherein the signal received via the third UL carrier is beamformed.

21. The method of claim 15 , wherein the first DL carrier is in an unlicensed band and the third UL carrier is in a licensed band, and wherein the unlicensed band is only used by the OFDM communication system for downlink communication.

22. The method of claim 15 , further comprising exchanging with a second base station via a wired backbone link, radio resource allocation information for the mobile device, and internet data or multimedia data for the mobile device.

23. A base station in an orthogonal frequency division multiplex (OFDM) communication system that utilizes two or more carriers for communication with a plurality of mobile devices, the base station comprising:

a transmitter configured to:

transmit broadcast information indicating a plurality of carriers for communication; and

transmit, to a mobile device, a first signal via a first downlink (DL) carrier of the plurality of carriers and a second signal simultaneously via a second DL carrier of the plurality of carriers, wherein the first DL carrier has a wider bandwidth than the second DL carrier and the first signal received via the first DL carrier has an increased subcarrier spacing in frequency and shorter OFDM symbols in time than the second signal received via the second DL carrier, wherein the first DL carrier is a different carrier than the second DL carrier; and

receiving, from the mobile device, a signal via a third uplink (UL) carrier of the plurality of carriers.

24. The base station of claim 23 , wherein the transmitter is further configured to transmit a message including system information via the second DL carrier, the message indicating that the third UL carrier is paired to the second DL carrier.

25. The base station of claim 23 , wherein the first DL carrier is a time division duplex (TDD) carrier and the third UL carrier is a same frequency carrier as the first DL carrier.

26. The base station of claim 23 , wherein the transmitter is further configured to:

periodically transmit synchronization signals used for time and frequency synchronization for the second DL carrier; and

transmit an indication of a cell identity associated with the second DL carrier.

27. The base station of claim 23 , wherein the second DL carrier is a primary DL carrier and the first DL carrier is an auxiliary DL carrier.

28. The base station of claim 23 , wherein the UL carrier is at a higher frequency than the second DL carrier, wherein the second signal is spatial multiplexed, and wherein the signal received via the third UL carrier is beamformed.

29. The base station of claim 23 , wherein the first DL carrier is in an unlicensed band and the third UL carrier is in a licensed band, and wherein the unlicensed band is only used by the OFDM communication system for downlink communication.

30. The base station of claim 23 , wherein the base station further comprises a transceiver configured to exchange, with a second base station via a wired backbone link, radio resource allocation information for the mobile device, and internet data or multimedia data for the mobile device.