Method and apparatus for transmitting data

1. A method for transmitting data, comprising:

performing, by a base station, a clear channel assessment (CCA) in a channel of an unlicensed band;

determining, by the base station, whether the channel is occupied in a first time period according to a CCA measurement value in the channel; and

determining, by the base station, a transmission power allowed during a second time period occupied by the channel according to a relationship between the CCA measurement value and a maximum transmission power,

wherein the second time period is next to the first time period.

2. The method of claim 1 ,

wherein the allowed transmission power is determined by comparing the CCA measurement value with a CCA threshold level.

3. The method of claim 1 , wherein the performing the CCA further comprises:

performing, by the base station, a CCA check; and

recording, by the base station, CCA measurement values, and

wherein the determining of the transmission power allowed during the second time period occupied by the channel comprises:

obtaining a maximum value among N smallest CCA measurement values as a first CCA threshold level according to the recorded CCA measurement values; and

determining the transmission power allowed during the second time period according to a relationship between the first CCA threshold level and the maximum transmission power.

4. The method of claim 1 , further comprising:

detecting CCA measurement values of at least two types of signals,

obtaining the CCA measurement values of the at least two types of signals as a first CCA threshold levels, and

determining allowed transmission powers according to a relationship between the first CCA threshold levels and the maximum transmission power,

wherein the maximum transmission power is a minimum value of the allowed transmission powers of the at least two types of signals.

5. The method of claim 4 , wherein the CCA measurement values of the at least two types of signals comprise:

an energy density of recognizable signals from an communication system and an energy density of other signals; or

energy of recognizable signals from a communication system of a first operator of the base station, energy of recognizable signals from a communication system of a second operator different from the first operator, and energy of other signals.

6. The method of claim 1 , wherein the allowed maximum transmission power comprises,

a maximum value of transmission powers on orthogonal frequency division multiplexing (OFDM) symbols or single carrier frequency division multiple access (SCFDMA) symbols in the second time period; or

a maximum value of average transmission powers of subframes in the channel second time period; or

a maximum value of an instant transmission power in the second time period.

7. The method of claim 6 ,

wherein the transmission power on each OFDM symbol is unchanged or decreases with time, in one channel occupancy time; or

wherein the average transmission power of each subframe is unchanged or decreases with time, in one channel occupancy time.

8. The method of claim 7 , wherein the transmission powers on OFDM symbols in one subframe have a difference within a configured first range.

9. The method of claim 7 , wherein the average transmission powers of subframes have a difference within a configured second range.

10. The method of claim 1 , further comprising:

if the CCA measurement value is lower than a CCA threshold value, occupying, by the base station, the channel to transmit a signals of a type, wherein the CCA threshold level is determined according to the type of the signal to be transmitted in the channel.

11. The method of claim 1 , further comprising:

obtaining a power boosting proportion of a physical downlink shared channel (PDSCH) in OFDM symbols containing zero power channel state indication-reference signal (ZP CSI-RS) according to a configuration of higher layer signaling.

12. The method of claim 1 , further comprising:

transmitting, by the base station, dummy signals.

13. A base station for transmitting data, comprising:

a transmitter configured to transmit the data; and

at least one processor configured to:

perform a clear channel assessment (CCA) in a channel of an unlicensed band,

determine whether the channel is occupied in a first time period according to a CCA measurement value in the channel, and

determine a transmission power allowed during a second time period occupied by the channel according to a relationship between the CCA measurement value and a maximum transmission power,

wherein the second time period is next to the first time period.

14. The base station of claim 13 ,

wherein the allowed transmission power is determined by comparing the CCA measurement value with a CCA threshold level.

15. The base station of claim 13 ,

wherein the at least one processor is further configured to:

perform a CCA check, and record the CCA measurement values, and

obtain a maximum value among N smallest CCA measurement values as a first CCA threshold level according to the recorded CCA measurement values, and determine the transmission power allowed during the second time period according to a relationship between the first CCA threshold level and the maximum transmission power.

16. The base station of claim 13 , wherein the at least one processor is further configured to:

detect CCA measurement values of at least two types of signals, and

obtain the CCA measurement values of the at least two types of signals as first CCA threshold levels, and determine allowed transmission powers according to a relationship between the first CCA threshold levels and the maximum transmission power, and

wherein the maximum transmission power is a minimum value of the allowed transmission powers of the at least two types of signals.