WO2014146613A1

WO2014146613A1 - Calibration signal transmission method and base station

Info

Publication number: WO2014146613A1
Application number: PCT/CN2014/073928
Authority: WO
Inventors: 易雄书; 张超超
Original assignee: 华为技术有限公司
Priority date: 2013-03-22
Filing date: 2014-03-24
Publication date: 2014-09-25
Also published as: CN104065449A

Abstract

Disclosed in an embodiment of the present invention are a calibration signal transmission method and base station, the method comprising: in a time division duplexing (TDD) system, when joint calibration is required between a first remote radio frequency unit of a first base station and a second remote radio frequency unit of a second base station, the first base station selects a non-pilot time slot having a length greater than or equal to the length of two OFDM symbols in a downlink pilot time slot DwPTS of a radio frame as a time slot for transmitting a joint calibration signal; the first base station transmits the joint calibration signal to the second base station at the selected non-pilot time slot. The length of the non-pilot time slot in the DwPTS is greater than or equal to the length of two OFDM symbols, thus satisfying the quality requirement for joint calibration signal transmission.

Description

Correction signal transmission method and base station

Technical field

The present invention relates to the field of communications, and in particular, to a method for transmitting a correction signal and a base station.

Background technique

In the Time Division Duplexing (TDD) system, the base station estimates the uplink channel by detecting the Sounding Reference Signal (SRS) sent by the terminal (UE), and utilizes the reciprocity of the uplink and downlink of the TDD system. The beamforming is performed by using the estimated uplink channel as a downlink channel. Although the TDD system is theoretically reciprocal in the uplink and downlink, in the actual system, the uplink and downlink channels respectively introduce different RF channels of the base station, and the responses of these RF channels are different, which requires channel correction. These channels are compensated. At present, there is a mature method for channel correction of a single cell. Through theoretical analysis, it is found that only the ratio of the uplink/downlink RF channels corresponding to each antenna is equal to the same value, which can meet the requirements of beamforming. Coordinative Multiple Point (CoMP) is a key feature of Long Term Evolution (LTE). CoMP technology can effectively combat the interference problem at the edge of LTE cell. Joint Transmission (JT) technology, as a type of CoMP technology, can significantly improve cell edge and average throughput. In order to achieve the gain brought by JT technology in the TDD system, channel correction is also required. Different from the single-cell beamforming technology, the JT technology requires that the ratio of the uplink and downlink RF channels corresponding to each antenna of multiple cells is the same. Even if each cell performs channel correction separately, if there is no inter-cell Correction, JT technology still can't reach the desired performance. Therefore, joint correction between cells is required for JT. Referring to FIG. 1, if the cell 2 of the base station 1 and the cell 1 of the base station 2 (where the arrow represents the main lobe transmission direction of the antenna) perform COMP JT transmission to serve a certain user, in order to achieve the desired performance of the JT, A joint correction is required between a remote radio unit (RRU) of cell 2 of base station 1 and a remote radio unit of cell 1 of base station 2.

Taking two cells as JTs as an example, the remote radio unit corresponding to cell 0 is RRU0, the corresponding base station is base station 0, the remote radio unit corresponding to cell 1 is RRU1, and the corresponding base station is base station 1.

The process is roughly as follows:

Step 1: The base station corresponding to RRU0 and RRU1 performs a single cell calibration procedure;

A method for performing self-correction in a single RRU is a prior art, and details are not described in this embodiment. After the self-correction of RRU0 and RRU1, the self-correction coefficients of the RF channel (including the service receiving channel and the service sending channel) in each service are obtained. The self-correcting coefficient includes the self-correcting coefficient of the service sending channel (referred to as the self-correcting coefficient). And the self-correction coefficient of the service receiving channel (referred to as the self-correction coefficient). By using the received correction coefficient and the self-correction coefficient to compensate the uplink reception and the downlink transmission respectively, the requirements of the TDD system for the uplink and downlink reciprocity of a single RRU can be satisfied. The received correction coefficient (") can be expressed as: The acceptance correction factor for k=0 is:

Κ ψ) 收^η k=i The acceptance correction factor is:

Where k is the kth RRU. In this embodiment, when k is 0, it represents RRUO, when k is 1, it represents RRU1; n represents the nth subcarrier, and η=0,1,...,Ν-1, N represents The number of subcarriers; i indicates the i-th service receiving channel, ) indicates the correcting channel of the kth RRU (correction channel, including the correction channel and the correction channel), which may be the internal RF channel of the RRU or all or part of the reuse The RF channel in the service may also be a medium RF channel independent of other independent devices other than the RRU. The channel response on the nth subcarrier; the i th service receiving channel representing the kth RRU is on the nth subcarrier. Channel response. The self-correction factor can be expressed as:

The self-correction coefficient at k=0 is: (η

The self-correction coefficient for { ^η ) Α ^η k = l is: ° ^L H = ( , n, ) h _l ... _j n) where k represents the kth RRU, and in this embodiment, k is 0, indicating RRUO When k is 1, it represents RRU1; n represents the nth subcarrier, η=0,1,...,Ν-1, ; i represents the ith transmission channel, and h _k ^c » represents the correction of the kth RRU. Channel response of the channel on the nth subcarrier; indicating the kth

The channel response of the i-th service transmission channel of the RRU on the n-th sub-carrier.

Step 2: Base station 0 controls RRUO to transmit a joint correction signal between RRUs through antenna 0 to antenna 0 corresponding to RRU1, and base station 1 controls RRU1 to jointly detect RRUs transmitted through antenna 0. The signal is sent to the antenna 0 corresponding to the RRUO, and the base station 0 and the base station 1 calculate the inter-RRU compensation coefficient between the RRUO and the RRU1 by using the received correction signal, and use the obtained inter-RRU compensation coefficient to update the single cell compensation corresponding to the radio channel in the RRU1 or RRUO transceiving. coefficient.

The frequency domain channel response obtained by using the base station 0 to receive the channel for channel estimation is denoted as h», and the frequency domain channel response obtained by using the base station 0 to receive the signal for channel estimation is recorded as the inter-RRU between h ₀ (n) and (n). Compensation coefficient γ _η , , update RRU1 received correction

The coefficient is: β» β» · γ(^ , the self-correction coefficient remains unchanged; or the update self-correction coefficient of RRU1 is: , the received correction coefficient remains unchanged;

The method can be extended to a scenario in which a single cell uses multiple RRUs to perform signal transmission and reception.

Currently, the transmission of the joint correction signal between the RRUs between the cells is performed within the guard time (GP) between the uplink and the downlink of the TDD radio frame (ie, the foregoing second step or the third step is completed in the GP). . It should be noted that, because the GP has a downlink pilot time slot DwPTS in front of it, and an uplink pilot time slot UpPTS is followed by the base station, if the base station performs downlink service transmission through the service transmission channel, it needs to use the service receiving channel to receive, considering Wave effects, it is necessary to reserve a certain timing in the GP to avoid the echo effect between the DwPTS and UpPTS service data. It is found through experiments that when the GP includes only one Orthogonal Frequency Division Multiplexing (OFDM) technology. When the symbol is reserved, the quality requirements for the joint correction signal transmission cannot be satisfied under the premise that a certain time is reserved for the DwPTS and the UpPTS, respectively.

Summary of the invention

Embodiments of the present invention provide a method and apparatus for correcting signals, which can ensure the quality of joint correction signal transmission when performing joint correction. A first aspect of the present invention provides a method for transmitting a correction signal, which may include: performing joint correction between a first remote radio unit of a first base station and a second remote radio unit of a second base station in a time division duplex system The first base station selects a non-pilot time slot having a length greater than or equal to 2 OFDM symbol lengths in a downlink pilot time slot DwPTS of the radio frame as a time slot for transmitting the joint correction signal;

The first base station transmits the joint correction signal to the second base station in the selected non-pilot time slot.

With reference to the first aspect, in a first possible implementation, the length of the guard time GP in the special subframe in which the downlink pilot time slot DwPTS is located is equal to one OFDM symbol length.

With reference to the first aspect, in a second possible implementation manner, the length of the downlink pilot time slot DwPTS is greater than three OFDM symbol lengths.

With reference to the first aspect to any one of the second possible implementation manners of the first aspect, in a third possible implementation manner, the joint correction signal has a length of 1 OFDM symbol length.

A second aspect of the present invention provides a base station, which may include:

a selection module, in the time division duplex system, when the first remote radio unit of the base station and the second remote radio unit of another base station need to perform joint correction, the length of the downlink pilot time slot DwPTS of the selected radio frame is greater than Or a non-pilot time slot equal to 2 OFDM symbol lengths as a time slot for transmitting a joint correction signal; And an antenna module, configured to send the joint correction signal to the another base station in a non-pilot time slot selected by the selection module. With reference to the second aspect, in a first possible implementation, the length of the guard time GP in the special subframe in which the downlink pilot time slot DwPTS selected by the selecting module is located is equal to 1 OFDM symbol length. With reference to the second aspect, in a second possible implementation, the length of the downlink pilot time slot DwPTS selected by the selecting module is greater than 3 OFDM symbol lengths. With reference to the second aspect to any one of the second possible implementation manners of the first aspect, in a third possible implementation manner, the joint correction signal has a length of 1 OFDM symbol length. It can be seen that, in some feasible embodiments of the present invention, in the time division duplex system, when the first remote radio unit of the first base station and the second remote radio unit of the second base station need to perform joint correction, The first base station selects a non-pilot time slot whose length is greater than or equal to 2 OFDM symbol length in the downlink pilot time slot DwPTS of the radio frame as a time slot for transmitting the joint correction signal; the first base station is in the selected non- The pilot time slot transmits the joint correction signal to the second base station. Since the length of the non-pilot slots in the DwPTS is greater than or equal to 2 OFDM symbols, this is sufficient to meet the transmission quality requirements of the joint correction signal.

DRAWINGS

1 is a schematic diagram showing a distribution of a base station and a cell in a mobile communication network; 2 is a schematic structural diagram of a radio frame according to the present invention; FIG. 3 is a schematic flowchart of an embodiment of a method for transmitting a correction signal according to the present invention; FIG. 4 is a diagram showing a pilot pattern of a special subframe under one antenna; 5 is a schematic structural diagram of an embodiment of a base station according to the present invention. detailed description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings. 2 is a schematic structural diagram of a radio frame of the present invention. As shown in FIG. 2, each radio frame includes 2 fields, where subframe 0 to subframe 4 are the previous field, and subframe 5 to subframe 9 are the next field, where subframe 1 and subframe 6 are The special subframe includes a downlink pilot time slot DwPTS, a guard time GP, and an uplink pilot time slot UpPTS. When the subframe configuration is performed, the configuration of the two special subframes can be as shown in Table 1 (the unit in Table 1 is an OFDM symbol, for example, 10 in the column of the GP, and the length of the GP is 10 OFDM, 1 Indicates that the length of the GP is 1 OFDM): Table 1 (below the normal cyclic check (CP, cyclic prefix) as an example;):

It can be seen from Table 1 that in some cases, the configured GP is exactly one OFDM in length, and therefore, in consideration of the influence of the echo, the GP of a single OFDM length cannot satisfy the quality requirement of the joint correction signal transmission.

Therefore, the embodiment of the present invention proposes a completely new method for transmitting a correction signal, which is used to compensate the GP of a single OFDM symbol as a shortage of the transmission time of the joint correction signal. Specifically, FIG. 3 is a schematic flowchart diagram of an embodiment of a method for transmitting a correction signal according to the present invention. The method may include: Step S110: In a time division duplex system, when the first remote radio unit of the first base station and the second remote radio unit of the second base station need to perform joint correction, the first base station selects a downlink of the radio frame. a non-pilot time slot having a length greater than or equal to 2 OFDM symbol lengths in the pilot time slot DwPTS as a time slot for transmitting a joint correction signal;

Step S111, the first base station (which may be the base station 1 or the base station 2 in FIG. 1) sends the joint correction signal to the second base station in the selected non-pilot time slot (when the first base station is In the case of the base station 1 in FIG. 1, the second base station herein may be the base station 2; when the first base station is the base station 2 in FIG. 1, the second base station herein may be the base station 1).

In some feasible implementation manners, in step S110, the length of the guard time GP in the special subframe in which the downlink pilot time slot DwPTS selected by the first base station is located is equal to 1 OFDM symbol length. Referring to Table 1, when the length of the GP is equal to one OFDM symbol, the length of the preceding DwPTS is 11 and 12 OFDM symbols, respectively. Further, FIG. 4 shows a pilot pattern of a special subframe under one antenna. In FIG. 4, 1=0, 1, ....6 appears twice, wherein the previous one is 0, 1 , ....6, represents the first slot of the special subframe, the latter 1=0, 1, ....6, indicating the second slot of the special subframe, each column in Figure 4 represents a The OFDM symbol duration, from which it can be seen that a special subframe includes 14 OFDM durations. Where R ₀ is the pilot and cannot be occupied by the correction signal.

Referring to Table 1, when the length of the DwPTS is 11 OFDM symbols, corresponding to FIG. 4, the first slot and the second slot are 1=0, 1, 2, and 3 are DwPTS, so that it can be seen that when the GP is When the length is equal to one OFDM symbol, 1=1, 2, 3, 5, 6 of the first slot in DwPTS is idle, 1=1, 2, 3 of the second slot are idle, and the first slot is idle. The length of 1=1-3 is 3 OFDM, the length of 1=5-6 is 2 OFDM, and the length of 1=1-3 of the second slot is 3 OFDM. When the length of the DwPTS is 12 OFDM symbols, corresponding to FIG. 4, the first slot and the second slot are 1=0, 1, 2, 3, 4 are DwPTS, and thus, it can be seen that when the GP is When the length is equal to one OFDM symbol, the first one in DwPTS 1=1, 2, 3, 5, and 6 of the slot are idle, 1=1, 2, and 3 of the second slot are idle, and the length of 1=1-3 of the first slot is 3 OFDM, 1 The length of =5-6 is 2 OFDM, and the length of 1=1-3 of the second slot is 3 OFDM; it has been experimentally proved that two or more OFDM lengths are considered in consideration of the influence of echoes. The time slots can meet the quality requirements of the joint correction signal transmission. Therefore, in a specific implementation, when the length of the GP is equal to one OFDM symbol, the length of the non-pilot slot in the DwPTS is greater than or equal to the length of the two OFDMs. Therefore, the length of the guard time GP in the radio frame is selected to be equal to one. The non-pilot time slot in the DwPTS in the subframe of the OFDM symbol serves as a time slot for transmitting the joint correction signal, which satisfies the quality requirement of the joint correction signal transmission.

In some possible implementations, in step S110, the length of the selected downlink pilot time slot DwPTS is greater than 3 OFDM symbol lengths. With reference to Table 1 and FIG. 4, when the length of the downlink pilot time slot DwPTS is greater than 3 OFDM symbol lengths, non-pilot OFDM symbols having a length equal to or greater than 2 OFDM symbol lengths can always appear in the DwPTS, and therefore, the length is greater than The DwPTS of 3 OFDM symbol lengths can always meet the quality requirements of the joint correction signal transmission.

In some feasible implementations, the length of the joint correction signal may be 1 OFDM symbol length, and the length of the joint correction signal is less than or equal to the time slot of the joint correction signal, which is the length of time occupied by the actual transmission correction signal.

It can be seen from the above that in some feasible embodiments of the present invention, in a time division duplex system, When the first remote radio unit of the first base station and the second remote radio unit of the second base station need to perform joint correction, the length of the downlink pilot time slot DwPTS of the first base station selecting the radio frame is greater than or equal to 2 OFDM. The symbol length non-pilot time slot is used as a time slot for transmitting a joint correction signal; the first base station transmits the joint correction signal to the second base station in the selected non-pilot time slot. Since the length of the non-pilot slots in the DwPTS is greater than or equal to 2 OFDM symbols, this is sufficient to meet the transmission quality requirements of the joint correction signal.

In a specific implementation, the method of the embodiment of the present invention is applicable to the second step and the third step described in the background, for improving the insufficiency of joint correction between cells in the background art.

As shown in FIG. 5, the base station (which may be the base station 1 or the base station 2 in FIG. 1) provided by the embodiment of the present invention may include: a selecting module 51 and an antenna module 52, where:

The selecting module 51 is configured to select, in the time division duplex system, the length of the downlink pilot time slot DwPTS of the radio frame when the first remote radio unit of the base station and the second remote radio unit of another base station need to perform joint correction. a non-pilot time slot greater than or equal to 2 OFDM symbol lengths as a time slot for transmitting a joint correction signal;

The antenna module 52 is configured to send the joint correction signal to the another base station in the non-pilot time slot selected by the selection module 51 (when the base station of the current plane is the base station 1 in FIG. 1, the other part here A base station may be the base station 2; when the previous base station is the base station 2 in FIG. 1, the other base station herein may be the base station 1). In some feasible implementation manners, the length of the guard time GP in the special subframe in which the downlink pilot time slot DwPTS selected by the selecting module 51 is located is equal to 1 OFDM symbol length. Referring to Table 1, when the length of the GP is equal to one OFDM symbol, the length of the preceding DwPTS is 11 and 12 OFDM symbols, respectively. Further, FIG. 4 shows a pilot pattern of a special subframe under one antenna. In FIG. 4, 1=0, 1, ....6 appears twice, wherein the previous one is 0, 1 , ....6, indicating the first slot of the special subframe, the latter 1=0, 1, ....6, indicating the second slot of the special subframe, each column in Figure 4 represents one The duration of the OFDM symbol, it can be seen that a special subframe includes 14 OFDM durations. The RQ is the pilot and cannot be occupied by the correction signal.

Referring to Table 1, when the length of the DwPTS is 11 OFDM symbols, corresponding to FIG. 4, the first slot and the second slot are 1=0, 1, 2, and 3 are DwPTS, so that it can be seen that when the GP is When the length is equal to one OFDM symbol, 1=1, 2, 3, 5, 6 of the first slot in DwPTS is idle, 1=1, 2, 3 of the second slot are idle, and the first slot is idle. The length of 1=1-3 is 3 OFDM, the length of 1=5-6 is 2 OFDM, and the length of 1=1-3 of the second slot is 3 OFDM. When the length of the DwPTS is 12 OFDM symbols, corresponding to FIG. 4, the first slot and the second slot are 1=0, 1, 2, 3, 4 are DwPTS, and thus, it can be seen that when the GP is When the length is equal to one OFDM symbol, 1=1, 2, 3, 5, 6 of the first slot in the DwPTS is idle, and 1=1, 2, 3 of the second slot are idle, and the first slot is idle. 1=1-3 is 3 OFDM in length, 1=5-6 is 2 OFDM in length, The length of 1=1-3 of the two slots is 3 OFDM; it has been experimentally proved that two or more OFDM-length time slots can satisfy the quality of joint correction signal transmission considering the influence of echo. Claim. Therefore, in a specific implementation, when the length of the GP is equal to one OFDM symbol, the length of the non-pilot slot in the DwPTS is greater than or equal to the length of the two OFDMs. Therefore, the length of the guard time GP in the radio frame is selected to be equal to one. The non-pilot time slot in the DwPTS in the subframe of the OFDM symbol serves as a time slot for transmitting the joint correction signal, which satisfies the quality requirement of the joint correction signal transmission.

In some possible implementation manners, the length of the downlink pilot time slot DwPTS selected by the selecting module 51 is greater than 3 OFDM symbol lengths. Referring still to Table 1 and FIG. 4, when the length of the downlink pilot time slot DwPTS is greater than 3 OFDM symbol lengths, a non-pilot having a length equal to or greater than 2 OFDM symbol lengths can always appear in the DwPTS, and therefore, the length is greater than 3 OFDM. The symbol length DwPTS always satisfies the quality requirements of the joint correction signal transmission.

In some possible implementations, the length of the joint correction signal transmitted by the antenna module 52 may be 1 OFDM symbol length. It can avoid the problem that the subcarrier spacing is easily affected by multipath when using 1/4 OFDM symbol length in the prior art (1/4 OFDM symbol length subcarrier spacing is 60 kHz, and subcarriers of 1 OFDM symbol length) The interval is 15 kHz).

The above are only the preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, and the equivalent changes made in the claims of the present invention are still within the scope of the present invention.

Claims

claims

1. A method of sending a correction signal, characterized by including:

In a time division duplex system, when joint correction is required between the first remote radio frequency unit of the first base station and the second remote radio frequency unit of the second base station, the first base station selects the downlink pilot time slot DwPTS of the radio frame. Non-pilot time slots with a length greater than or equal to 2 OFDM symbol lengths are used as time slots for transmitting joint correction signals;

The first base station sends the joint correction signal to the second base station in the selected non-pilot time slot.

2. The correction signal sending method according to claim 1, characterized in that the length of the guard time GP in the special subframe where the downlink pilot time slot DwPTS is located is equal to the length of 1 OFDM symbol.

3. The correction signal sending method according to claim 1, characterized in that the length of the downlink pilot time slot DwPTS is greater than 3 OFDM symbols.

4. The correction signal transmission method according to any one of claims 1 to 3, characterized in that the length of the joint correction signal is one OFDM symbol length.

5. A base station, characterized by including:

A selection module configured to select the downlink pilot time slot DwPTS of the wireless frame with a length greater than Or a non-pilot time slot equal to the length of 2 OFDM symbols is used as the time slot for transmitting the joint correction signal;

The antenna module is configured to send the joint correction signal to the other base station in the non-pilot time slot selected by the selection module.

6. The base station according to claim 5, characterized in that the length of the guard time GP in the special subframe where the downlink pilot time slot DwPTS selected by the selection module is located is equal to the length of 1 OFDM symbol.

7. The base station according to claim 5, wherein the length of the downlink pilot time slot DwPTS selected by the selection module is greater than 3 OFDM symbols.

8. The base station according to claims 5-7, characterized in that the length of the joint correction signal is one OFDM symbol length.