Pilot signal transmitting method, and channel estimation method, apparatus, and system

1. A pilot signal transmitting method for transmitting a pilot signal in a multiple-input multiple-output (MIMO) system, the method comprises:

within a transmission time interval (TTI), transmitting a first pilot signal (CPICH 1 ) on a first antenna, and transmitting at least a portion of a second pilot signal (CPICH 2 ) on a second antenna; and

when no first-type terminal is scheduled within coverage of the MIMO system within the TTI, transmitting a third pilot signal (CPICH 3 ) on a third antenna, and transmitting a fourth pilot signal (CPICH 4 ) on a fourth antenna;

when no legacy terminal is scheduled within coverage of the MIMO system within the TTI, decomposing the CPICH 2 into a CPICH 2 s and a CPICH 2 e and, when no first-type terminal is scheduled within coverage of the MIMO system within the TTI, transmitting the CPICH 2 s but not the CPICH 2 e on the second antenna;

wherein the CPICH 1 is used for channel state information (CSI) estimation and data demodulation, the CPICH 2 is used for CSI estimation and data demodulation, CPICH 2 s is a pilot signal required for performing CSI estimation, the CPICH 2 e is a pilot signal required for performing data demodulation, the CPICH 3 is a pilot signal required for performing CSI estimation, and the CPICH 4 is a pilot signal required for performing CSI estimation, the MIMO system comprises a 4 Branch MIMO system or an 8 Branch MIMO system, the first-type terminal is a 4 Branch MIMO terminal corresponding to the 4 Branch MIMO system, or a 4 Branch MIMO terminal or an 8 Branch MIMO terminal corresponding to the 8 Branch MIMO system, and wherein the legacy terminal is one of a single-input single-output terminal, a single-input 2-output terminal, or a 2 Branch MIMO terminal.

2. The method according to claim 1 , further comprising:

when a first-type terminal is scheduled within the coverage of the MIMO system within the TTI, transmitting the CPICH 2 e on the second antenna, transmitting the CPICH 3 and a fifth pilot signal (CPICH 5 ) on the third antenna, and transmitting the CPICH 4 and a sixth pilot signal (CPICH 6 ) on the fourth antenna, wherein the CPICH 5 is a pilot signal required for performing data demodulation, and the CPICH 6 is a pilot signal required for performing data demodulation.

3. The method according to claim 1 , wherein transmitting a third pilot signal (CPICH 3 ) on a third antenna, and transmitting a fourth pilot signal (CPICH 4 ) on a fourth antenna, comprises:

sending the CPICH 3 and the CPICH 4 through two code channels; or

sending the CPICH 3 and the CPICH 4 through one code channel according to two orthogonal space-time block coding based transmit diversity (STTD) pilot patterns.

4. The method according to claim 2 , wherein transmitting the CPICH 3 and a fifth pilot signal (CPICH 5 ) on the third antenna, and transmitting the CPICH 4 and a sixth pilot signal CPICH 6 on the fourth antenna, comprises any of:

sending the CPICH 3 and the CPICH 5 through two code channels, and combining the CPICH 4 and the CPICH 6 into one pilot signal (CPICH 4 ′) and sending the CPICH 4 ′ through another code channel;

combining the CPICH 3 and the CPICH 5 into one pilot signal (CPICH 3 ′) and sending the CPICH 3 ′ through one code channel, and combining the CPICH 4 and the CPICH 6 into another pilot signal (CPICH 4 ′) and sending the CPICH 4 ′ through another code channel;

sending the CPICH 3 and the CPICH 4 through two code channels, and sending the CPICH 5 and the CPICH 6 through another code channel according to two orthogonal space-time block coding based transmit diversity pilot (STTD) patterns; and

sending the CPICH 3 and the CPICH 4 through one code channel according to two orthogonal STTD patterns, and sending the CPICH 5 and the CPICH 6 through another code channel according to two orthogonal space-time block coding based transmit diversity (STTD) patterns.

5. The method according to claim 2 , further comprising:

separately determining, according to transmit powers required by all first-type terminals within the coverage of the MIMO system for performing CSI estimation and channel estimation that is used for data demodulation, a transmit power for transmitting the CPICH 3 and the CPICH 5 on the third antenna and a transmit power for transmitting the CPICH 4 and the CPICH 6 on the fourth antenna.

6. The method according to claim 1 , wherein:

time sequence boundaries of the CPICH 1 , the CPICH 2 , the CPICH 3 , and the CPICH 4 are aligned with a time sequence boundary of a primary common control physical channel (P-CCPCH); and

time sequence boundaries of the CPICH 5 and the CPICH 6 are aligned with a time sequence boundary of a high speed physical downlink shared channel (HS-PDSCH) that is two timeslots later than the CPICH 1 , the CPICH 2 , the CPICH 3 , and the CPICH 4 .

7. A communications base station, comprising: a first antenna, a second antenna, a third antenna, a fourth antenna, and a pilot signal transmitting apparatus, wherein the pilot signal transmitting apparatus comprises:

a first transmitting unit, configured to:

within a transmission time interval (TTI), transmit a first pilot signal (CPICH 1 ) on the first antenna, and transmit at least a portion of a second pilot signal (CPICH 2 ) on the second antenna;

when no legacy terminal is scheduled within coverage of the MIMO system within the TTI, decompose the CPICH 2 into a CPICH 2 s and a CPICH 2 e and, when no first-type terminal is scheduled within coverage of the MIMO system within the TTI, transmit the CPICH 2 s but not the CPICH 2 e on the second antenna; and

a second transmitting unit, configured to:

when no first-type terminal is scheduled within coverage of a MIMO system within the TTI, transmit a third pilot signal (CPICH 3 ) on the third antenna, and transmit a fourth pilot signal (CPICH 4 ) on the fourth antenna;

wherein the CPICH 1 is used for channel state information (CSI) estimation and data demodulation, the CPICH 2 is used for CSI estimation and data demodulation, the CPICH 2 s is used for CSI estimation, the CPICH 2 e is used for data demodulation, the CPICH 3 is used for CSI estimation, and the CPICH 4 is used for CSI estimation, and wherein the legacy terminal is one of a single-input single-output terminal, a single-input 2-output terminal, or a 2 Branch MIMO terminal.

8. The base station according to claim 7 , wherein the pilot signal transmitting apparatus further comprises:

a third transmitting unit, configured to: when a first-type terminal is scheduled within the coverage of the MIMO system within the TTI, transmit the CPICH 3 and a fifth pilot signal (CPICH 5 ) on the third antenna, and transmit the CPICH 4 and a sixth pilot signal (CPICH 6 ) on the fourth antenna;

wherein the first transmitting unit is configured to transmit the CPICH 2 e on the second antenna when a first-type terminal is scheduled within the coverage of the MIMO system within the TTI;

wherein the CPICH 3 is used for CSI estimation, the CPICH 4 is used for CSI estimation, the CPICH 5 is used for data demodulation, and the CPICH 6 is used for data demodulation.

9. The base station according to claim 8 , wherein the pilot signal transmitting apparatus further comprises:

a transmit power determining unit, configured to:

separately determine a transmit power of the first transmitting unit on the first antenna and a transmit power of the first transmitting unit on the second antenna according to requirements of powers required by all terminals within the coverage for performing both CSI estimation and channel estimation that is used for data demodulation; and

separately determine a transmit power of the second transmitting unit on the third antenna and a transmit power of the second transmitting unit on the fourth antenna according to requirements of powers required by all first-type terminals within the coverage for performing CSI estimation; or separately determine, according to requirements of powers required by all first-type terminals within the coverage for performing both CSI estimation and channel estimation that is used for data demodulation, a transmit power for the third transmitting unit to transmit the CPICH 3 and the CPICH 5 on the third antenna and a transmit power for the third transmitting unit to transmit the CPICH 4 and the CPICH 6 on the fourth antenna.

10. The base station according to claim 7 , wherein:

the first transmitting unit is configured to send the CPICH 1 through a first code channel and send the CPICH 2 through a second code channel; and

the second transmitting unit is configured to send the CPICH 3 through a third code channel and send the CPICH 4 through a fourth code channel; or configured to send the CPICH 3 and the CPICH 4 through a third code channel according to two orthogonal space-time block coding based transmit diversity pilot patterns (STTD) patterns.

11. The base station according to claim 8 , wherein the third transmitting unit is configured to send any of:

the CPICH 3 through a third code channel, send the CPICH 5 through a fourth code channel, and send, through a fifth code channel, a pilot signal (CPICH 4 ′) that is obtained by combining the CPICH 4 and the CPICH 6 ;

through a third code channel, a pilot signal (CPICH 3 ′) that is obtained by combining the CPICH 3 and the CPICH 5 and send, through a fourth code channel, another pilot signal (CPICH 4 ′) that is obtained by combining the CPICH 4 and the CPICH 6 ;

the CPICH 3 through a third code channel, send the CPICH 4 through a fourth code channel, and send the CPICH 5 and the CPICH 6 through a fifth code channel according to two orthogonal space-time block coding based transmit diversity pilot patterns (STTD) patterns; and

the CPICH 3 and the CPICH 4 through a third code channel according to two orthogonal STTD patterns and send the CPICH 5 and the CPICH 6 through a fourth code channel according to two orthogonal STTD patterns.

12. The base station according to claim 8 , wherein the pilot signal transmitting apparatus further comprises:

a judging unit, configured to:

determine whether a first-type terminal is scheduled in the MIMO system within the TTI, and control, according to a result of the determining, the second transmitting unit or the third transmitting unit to transmit a pilot signal;

if no first-type terminal is scheduled in the MIMO system within the TTI, control the second transmitting unit to transmit a pilot signal; and

if a first-type terminal is scheduled in the MIMO system within the TTI, control the third transmitting unit to transmit a pilot signal.