CN101286754A - Method, communication device for acquiring channel information - Google Patents

Abstract

The invention relates to the field of communication and the embodiment of the invention discloses a method for obtaining channel information, and communication devices applied to the method. The method of the invention includes that: a first communication device receives a downlink pilot emitted by a second communication device and superimposes the received downlink pilot and an uplink pilot to generate a mixed pilot which is then sent to the second communication device; the second communication device receives the mixed pilot and carries out estimation to an uplink channel according to the received mixed pilot and the given uplink pilot so as to obtain the parameters of the uplink channel; the second communication device recovers to obtain the mixed pilot emitted by the first communication device according to the parameters of the uplink channel and then obtains the parameters of a downlink channel according to the mixed pilot emitted by the first communication device, the given uplink pilot and the given downlink pilot which are recovered to be obtained. The technical proposal of the embodiment of the invention can not only realize the estimation of the uplink channel and obtain the parameters of the downlink channel, but also reduce the cost on the feedback, compared with the prior art.

Description

Method for acquiring channel information and communication equipment

Technical Field

The present invention relates to the field of communications, and in particular, to a method and a communications device for acquiring channel information.

Background

In a wireless communication system, signals are affected by a transmission channel during transmission, and fading or distortion occurs, and a receiving end generally needs to estimate a transmission physical channel in order to recover the signals of a transmission source, and eliminate the influence of the channel on the transmission signals by an equalization method. Fig. 1 is a schematic diagram of a typical wireless communication structure, as shown in the figure, a transcoder 102 is used to encode a signal at a transmission source 101, a modulator 103 modulates the signal code, and sends the modulated signal to a channel 104, the signal is interfered by a noise source 105 and adds noise during transmission of the channel 104, the signal passes through the channel to reach a receiving end, and the receiving end performs 106: estimating and equalizing the channel 104 by using channel estimation pre-equalization to recover a signal transmitted by a transmitting end; then, the restored signal is demodulated by the demodulator 107, and the demodulated signal is decoded by the decoder 108 to be read.

However, due to the existence of additive noise at the receiving end, the equalization effect is often affected by the additive noise, for example: zero Forcing (ZF) equalizers can cause noise amplification at lower signal-to-noise ratios; although a Minimum Mean Square Error (MMSE) equalizer can effectively suppress the influence of noise, it needs to perform complex variance estimation operation on the noise at a receiving end; still others such as: the maximum likelihood detection algorithm and the like are not suitable for use in an actual system due to too large calculation amount.

For this reason, the prior art proposes an effective solution: the signal is preprocessed at a transmitting end, for example, the signal-Input Single-Output (SISO) system is preprocessed in a Single-transmit Single-receive antenna (SISO) system, and the precoding processing is needed in a Multiple-transmit Multiple-receive antenna (MIMO) system.

The following 3 points are the main benefits of preprocessing the signal at the transmitting end:

firstly, the method comprises the following steps: the transmitting end carries out corresponding preprocessing on the signals according to the characteristics of the transmission channel, thereby improving the fading of the channel and avoiding the amplification of noise when the receiving end processes a deep fading channel.

Secondly, the method comprises the following steps: in the downlink, the main processing of the signals can be placed at the transmitting end (such as a base station) by adopting the technology, so that the advantage of strong processing capability of the transmitting end can be fully utilized, and meanwhile, the processing burden of the receiving end (such as a terminal) with weak processing capability is greatly reduced, so that the receiving end can achieve good system performance only by simply processing the signals.

Thirdly, the method comprises the following steps: the transmitting end can implement a reasonable channel scheduling strategy according to the channel characteristics of each user.

The technical scheme of preprocessing signals at a transmitting end according to the characteristics of a transmission channel is a closed-loop precoding technology in an MIMO system, and the application of the technology can improve the performance of the system.

However, one of the main technical requirements for implementing pre-equalization in the downlink in SISO systems, or pre-processing for precoding etc. in MIMO systems is: the transmitting end needs to know the downlink channel.

In order to enable a transmitting end to acquire parameters of a downlink Channel, a technical scheme is provided in the current 802.20 standard, and specifically, a terminal estimates a forward link according to a forward common pilot, calculates a precoding matrix optimal for the terminal, and then feeds back an index number of the precoding matrix, a rank of the Channel, and a Channel Quality Indicator (CQI for short) of the downlink to a base station in a signaling form, where the base station may precode transmission data according to the fed-back information. In the feedback signaling specified in the standard, 6 bits are required for feeding back the index number of precoding, and 2 bits are required for feeding back the rank of the channel.

During the process of carrying out the present invention, the inventors of the present invention found that the technical solution provided in the current 802.20 standard has at least the following disadvantages:

1. the processing load of the terminal increases: the terminal needs to determine the codebook to be used according to the estimated downlink channel, and the calculation amount is large.

2. The correctness of the downlink information parameter fed back by the terminal to the transmitting end in the transmission process of returning to the base station of the transmitting end (base station) can not be ensured: due to the influence of channel fading, the parameters may be distorted during channel transmission, and the transmitting end (base station) cannot obtain correct downlink parameters.

In addition, in order to enable the transmitting end to acquire the parameters of the downlink channel and perform pre-equalization or pre-coding processing by using the parameters of the downlink channel, another technical scheme with a wider application exists in the prior art: the direct channel feedback strategy specifically comprises the following steps:

after receiving the downlink pilot signal, the terminal estimates the downlink channel to obtain parameters of the downlink channel, then encodes the estimated parameters of the downlink channel, and forms an Orthogonal Frequency Division Multiplexing (OFDM) symbol together with the uplink pilot to transmit to the base station, wherein the encoded downlink channel information occupies odd subcarriers of the OFDM symbol, the uplink pilot occupies even subcarriers of the OFDM symbol, after receiving the signal, the base station performs uplink channel estimation according to the uplink pilot of the even subcarriers, and recovers and obtains the parameters of the downlink channel transmitted by the terminal by using an estimation result of the uplink channel.

The inventor of the present invention finds the technical solution of the direct channel feedback strategy in the process of carrying out the present invention, and still has at least the following disadvantages:

after being coded, the downlink channel information is fed back to the base station by using odd subcarriers, and certain channel resources are occupied;

meanwhile, distortion still exists in the summary of the downlink channel parameters in the channel transmission process, so that the transmitting end cannot obtain correct parameters of the downlink channel.

Disclosure of Invention

The embodiment of the invention provides a method for acquiring channel information, which can estimate an uplink channel, acquire parameters of a downlink channel and reduce feedback overhead.

The embodiment of the invention also provides a method for acquiring the channel information, which realizes the estimation of the uplink channel, simultaneously acquires the parameters of the downlink channel and reduces the feedback overhead.

The embodiment of the invention also provides communication equipment, which reduces feedback overhead, so that the communication equipment at the opposite end can estimate the uplink channel and simultaneously acquire the parameters of the downlink channel.

The embodiment of the invention also provides communication equipment, which can estimate the uplink channel and simultaneously acquire the parameters of the downlink channel.

The embodiment of the invention also provides communication equipment, which can estimate the uplink channel and simultaneously acquire the parameters of the downlink channel.

The method for acquiring channel information provided by the embodiment of the invention can comprise the following steps:

the method comprises the steps that a first communication device receives a downlink pilot frequency sent by a second communication device, the received downlink pilot frequency and an uplink pilot frequency are overlapped to generate a mixed pilot frequency, and the mixed pilot frequency is sent to the second communication device;

the second communication equipment receives the mixed pilot frequency, estimates an uplink channel according to the received mixed pilot frequency and the known uplink pilot frequency, and acquires uplink channel parameters;

the second communication equipment estimates a closed-loop channel according to the known downlink pilot frequency and the received mixed pilot frequency to acquire closed-loop channel parameters;

and the second communication equipment acquires the downlink channel parameters according to the closed-loop channel parameters and the uplink channel parameters.

The method for acquiring channel information provided by the embodiment of the invention can comprise the following steps:

the method comprises the steps that a first communication device receives a downlink pilot frequency sent by a second communication device, the received downlink pilot frequency and an uplink pilot frequency are overlapped to generate a mixed pilot frequency, and the mixed pilot frequency is sent to the second communication device;

the second communication equipment receives the mixed pilot frequency, estimates an uplink channel according to the received mixed pilot frequency and the known uplink pilot frequency, and acquires uplink channel parameters;

the second communication equipment recovers and acquires the mixed pilot frequency transmitted by the first communication equipment according to the uplink channel parameters;

and the second communication equipment acquires the downlink channel parameters according to the recovered and acquired mixed pilot frequency, known uplink pilot frequency and known downlink pilot frequency transmitted by the first communication equipment.

The communication device provided by the embodiment of the invention can comprise:

a receiving unit, configured to receive a downlink pilot sent by a second communication device;

pilot frequency coding unit, which is used to superpose the received downlink pilot frequency and uplink pilot frequency to form mixed pilot frequency;

a sending unit, configured to send the hybrid pilot to the second communication device.

The communication device provided by the embodiment of the invention can comprise:

a downlink pilot frequency coding unit, configured to code a downlink pilot frequency issued to a second communication device, so that a form of the downlink pilot frequency in a time domain satisfies:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> <mo>+</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein said p is_dl ^i*(t) is downlink pilot p sent by antenna i of the communication device to the second communication device_dl ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by an antenna j of the communication equipment to the second communication equipment_dlFor the delay spread length, L, of the downlink channel_ulIs the delay spread length of the uplink channel, a is a real number greater than zero,

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0,0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> <mo>+</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> <mo>,</mo> </mrow> </math>

wherein, the p is_ul ^i*(t) uplink pilot p for transmission from antenna i of second communication device to this communication device_ul ⁱConjugation of (t), p_dk ^j(n-t) is a downlink pilot frequency (L) sent by an antenna j of the communication equipment to the second communication equipment_dlFor the delay spread length, L, of the downlink channel_ulA is a real number greater than zero and is the delay spread length of an uplink channel;

a sending unit, configured to send the downlink pilot generated by the downlink pilot encoding unit to the second communication device;

a receiving unit, configured to receive the hybrid pilot sent by the second communication device, where the hybrid pilot is: the second communication equipment receives superposition of the downlink pilot frequency and the uplink pilot frequency sent by the communication equipment;

an uplink channel estimation unit, configured to estimate an uplink channel according to the hybrid pilot and a known uplink pilot, and obtain an uplink channel parameter;

a closed-loop channel estimation unit, configured to estimate a closed-loop channel according to the received mixed pilot and a known downlink pilot, and obtain closed-loop channel parameters;

and the downlink channel estimation unit is used for acquiring the downlink channel parameters according to the closed-loop channel parameters and the uplink channel parameters.

The communication device provided by the embodiment of the invention can comprise:

a downlink pilot frequency coding unit, configured to code a downlink pilot frequency issued to a second communication device, so that a form of the downlink pilot frequency in a time domain satisfies:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein said p is_dl ^i*(t) is downlink pilot p sent by antenna i of the second communication device to the communication device_dl ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency, L, issued by the antenna j of the second communication device to the communication device_dlIs the delay spread length of the downlink channel, a is a real number greater than zero,

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0,0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> <mo>,</mo> </mrow> </math>

wherein, the p is_ul ^i*(t) uplink pilot p for transmission from antenna i of second communication device to this communication device_ul ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by an antenna j of the communication equipment to the second communication equipment_dlDelay spread length for downlink channel，L_ulA is a real number greater than zero and is the delay spread length of an uplink channel;

a sending unit, configured to send the downlink pilot generated by the downlink pilot encoding unit to the second communication device;

a receiving unit, configured to receive the hybrid pilot sent by the second communication device, where the hybrid pilot is: the second communication equipment receives superposition of the downlink pilot frequency and the uplink pilot frequency sent by the communication equipment;

an uplink channel estimation unit, configured to estimate an uplink channel according to the hybrid pilot and a known uplink pilot, and obtain an uplink channel parameter;

a mixed pilot recovery unit, configured to recover and acquire the mixed pilot sent by the second communication device according to the uplink channel parameter and the received mixed pilot;

and a downlink channel estimation unit, configured to obtain a downlink channel parameter according to the hybrid pilot, the known downlink pilot, and the known uplink pilot sent by the second communication device.

As can be seen from the foregoing technical solutions, in the technical solution of the embodiment of the present invention, after receiving the downlink pilot sent by the second communication device, the first communication device superimposes the received downlink pilot with the uplink pilot that needs to be sent to the second communication device, so as to generate a mixed pilot, and send the mixed pilot to the second communication device, so that after receiving the mixed pilot, the second communication device estimates and obtains parameters of the uplink channel and the downlink channel according to the mixed pilot and the known uplink pilot and downlink pilot. The second communication equipment estimates the uplink channel and simultaneously acquires the parameters of the downlink channel.

In addition, in the technical solution of the embodiment of the present invention, the first communication device sends the mixed pilot to the second communication device, so that the second communication device can obtain the downlink channel parameters while estimating and obtaining the uplink channel parameters, instead of performing corresponding estimation and corresponding precoding on the downlink pilot after the second communication device receives the downlink pilot as in the prior art, and then returning the result of the estimation processing to the second communication device, so that the second communication device obtains the parameters of the downlink channel. Compared with the prior art, the technical scheme of the embodiment of the invention reduces signaling overhead and saves transmission resources; compared with the prior art, the method and the device have the advantages that the downlink channel parameters are not required to be directly transmitted, so that the problem that the second communication device cannot obtain the correct downlink channel parameters due to distortion of the parameters caused by fading of a transmission channel is effectively solved.

In addition, the technical scheme of the embodiment of the invention is also favorable for placing more complex processing such as downlink channel estimation, precoding and the like on the side of the second communication equipment, and the effect is better and remarkable under the condition that the processing capability of the first communication equipment is relatively weaker.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

fig. 1 is a diagram illustrating a typical wireless communication transmission and reception in the prior art;

fig. 2 is a flowchart illustrating a method for obtaining channel information in a SISO system according to embodiment 1 of the present invention;

fig. 3 is a schematic flowchart of a method for obtaining channel information in an MIMO system according to embodiment 2 of the present invention;

fig. 4 is a flowchart illustrating another method for acquiring channel information applied in a SISO system according to embodiment 3 of the present invention;

fig. 5 is a schematic flowchart of another method for obtaining channel information in a MIMO system according to embodiment 4 of the present invention;

fig. 6 is a schematic structural diagram of a communication device provided in embodiment 5 of the present invention;

fig. 7 is a schematic structural diagram of another communication device provided in embodiment 5 of the present invention;

fig. 8 is a schematic structural diagram of a communication device provided in embodiment 6 of the present invention;

fig. 9 is a schematic structural diagram of a communication device provided in embodiment 7 of the present invention;

fig. 10 is a schematic structural diagram of a communication device provided in embodiment 8 of the present invention.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.

Example 1:

in this embodiment, taking an example of applying the method for acquiring channel information provided in the embodiment of the present invention in a SISO system, the method is specifically described, fig. 2 is a schematic flow chart of the method in this embodiment, as shown in fig. 2, the method may include:

step 201: and the second communication equipment transmits the downlink pilot frequency to the first communication equipment.

The second communication device carries out OFDM modulation on the downlink pilot frequency and the downlink data, and transmits the downlink pilot frequency and the downlink data from the transmitting antenna to a downlink channel for transmission after adding the CP: after the transmission data is coded and modulated, downlink pilot frequency is inserted into subcarriers with equal intervals in a frequency domain, and after OFDM modulation, CP is added to the modulated data and then the modulated data is transmitted from a transmitting antenna.

In order to prevent the downlink pilot in the mixed pilot in the technical solution of this embodiment from affecting the estimation of the uplink channel and the closed-loop channel by the first communication device, the uplink pilot and the downlink pilot between the first communication device and the second communication device may be preset, so that the uplink pilot and the downlink pilot respectively satisfy the following conditions:

(1) for the downlink pilot frequency sent by the second communication device to the first communication device, the time delay expansion length L of the convolution result of the sent downlink pilot frequency in the time domain on the uplink channel can be made_ulDelay spread length L with downlink channel_dlThe sum range is an impulse function, that is, the autocorrelation function of the downlink pilot frequency in the time domain can be represented in the form shown in the functional formula (1), so that the first communication device directly superimposes the received downlink pilot frequency and the uplink pilot frequency after receiving the downlink pilot frequency, and does not need to perform additional processing on the received downlink pilot frequency.

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msubsup> <mi>p</mi> <mi>dl</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msub> <mi>p</mi> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> <mo>+</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

Wherein p is_dl ^*(t) represents: uplink pilot frequency

Conjugation of (1); l is_dlRepresents: the delay spread length of the downlink channel; l is_ulRepresents: the delay spread length of the uplink channel; l is_dl+L_ulRepresents: the delay spread length of the closed-loop channel; a is a real number greater than zero, and a may be equal to 1 without loss of generality.

(2) For the uplink pilot frequency, the convolution result in the time domain of the uplink pilot frequency is the delay spread length L of the uplink channel_ulImpulse function in the range, that is, the autocorrelation function of the uplink pilot in the time domain can be represented as:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msubsup> <mi>p</mi> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msub> <mi>p</mi> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

wherein p is_ul ^*(t) represents: uplink pilot frequencyA is a real number greater than zero, and a can be made equal to 1 without loss of generality.

(3) For the uplink pilot frequency and the downlink pilot frequency, the convolution result of the uplink pilot frequency and the downlink pilot frequency has the delay expansion length L of the uplink channel_ulDelay spread length L with downlink channel_dlThe sum of which is zero. Namely:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msubsup> <mi>p</mi> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msub> <mi>p</mi> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0,0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> <mo>+</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow> </math>

the second communication equipment sends the downlink pilot frequency meeting the limitation of the functional expressions (1) and (3) to the first communication equipment, so that the second communication equipment directly superposes the received downlink pilot frequency and the received uplink pilot frequency after receiving the downlink pilot frequency without performing additional processing on the received downlink pilot frequency.

Step 202: the first communication equipment receives the downlink pilot frequency, superposes the received downlink pilot frequency and the uplink pilot frequency to generate a mixed pilot frequency, and sends the superposed mixed pilot frequency to the second communication equipment.

After receiving a signal sent by a second communication device, a first communication device extracts a signal on a corresponding pilot channel after the received signal is subjected to Cyclic Prefix (CP) and OFDM demodulation, and superimposes the extracted downlink pilot and an uplink pilot to be sent to the second communication device on a frequency domain to generate a mixed pilot. The hybrid pilot is: and superposing the downlink pilot frequency sent to the first communication equipment by the second communication equipment and the uplink pilot frequency sent to the second communication equipment by the first communication equipment. I.e., in an OFDM system, the hybrid pilot behaves as: in a subcarrier of an OFDM symbol, a downlink pilot transmitted from the second communication device to the first communication device via its downlink channel and an uplink pilot transmitted from the first communication device to the second communication device are included.

Wherein, the uplink pilot frequency sent by the first communication device to the second communication device satisfies the restriction conditions expressed by the preset functional expressions (2) and (3) in step 201.

After generating the mixed pilot frequency, the first communication device performs OFDM modulation on the superposed mixed pilot frequency and uplink data when transmitting the uplink data to the second communication device, performs uplink transmission after adding a CP, and transmits the uplink transmission to the second communication device.

When the first communication device transmits the mixed pilot to the second communication device, the mixed pilot can be transmitted by referring to a pilot transmission mode in the prior art, so that the powers allocated to the uplink pilot and the downlink pilot in the mixed pilot are simply equal.

However, in an actual system, if the downlink pilot is directly superimposed on the uplink pilot under the condition that the transmission power of the first communication device is limited, the transmission power of the first communication device needs to be greatly increased, and may even be larger than the upper limit of the transmission power of the first communication device, which is not favorable for implementation. In addition, the downlink pilot frequency brings convolution noise in the process of returning to the second communication device, and the noise is difficult to eliminate in the channel estimation process because the noise also passes through the uplink channel. Therefore, in the embodiment of the present invention, most of the power may be allocated to the uplink pilot, and a small part of the power may be allocated to the downlink pilot, which not only can ensure that the pilot (mixed pilot) transmission power of the first communication device does not exceed the predetermined upper transmission limit, but also can greatly suppress the convolution noise, thereby being beneficial to improving the accuracy of the estimation of the uplink channel by the second communication device at the opposite end.

This embodiment provides two optional technical solutions for allocating the transmission power of the downlink pilot and the uplink pilot when the first communication device transmits the hybrid pilot:

the first scheme is as follows: total power constant scheme

In the scheme, the total transmission power of the pilot subcarriers of the first communication device (the sum of the uplink pilot transmission power and the downlink pilot transmission power allocated to the subcarriers) is agreed to be constant, and the second communication device can be informed of the constant total transmission power after agreement.

Then, a power allocation factor α is defined, which is assumed here to be: the ratio of the power allocated to the downlink pilot frequency to the total power of the hybrid pilot frequency is, then the hybrid pilot signal transmitted on the uplink pilot frequency channel is: <math> <mrow> <msub> <mi>s</mi> <mi>p</mi> </msub> <mo>=</mo> <msqrt> <mi>&alpha;</mi> </msqrt> <mo>&CenterDot;</mo> <msubsup> <mi>p</mi> <mi>dl</mi> <mo>&prime;</mo> </msubsup> <mo>+</mo> <msqrt> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <mi>&alpha;</mi> <mo>)</mo> </mrow> </msqrt> <msub> <mi>p</mi> <mi>ul</mi> </msub> <mo>.</mo> </mrow> </math>

in this scheme, the first communication device may dynamically take a value of the power allocation factor α according to an actual situation, and transmit the power allocation factor α to the second communication device when sending the hybrid pilot, so that the second communication device can obtain the power allocation situation of the received hybrid pilot.

It should be noted that, in the present solution, the overhead occupied by the transmission power allocation factor α is very small, for example: two kinds of allocations of 0.1 or 0.25 of the total power occupied by the downlink pilot frequency are specified, and only 1 bit of information is needed to be transmitted.

Scheme II: uplink pilot power constancy scheme

In this scheme, for the power allocated to the uplink pilot, it may be negotiated to make the power allocated to the uplink pilot constant, and the second communication device may be notified of the constant value of the uplink pilot power; for the power allocated to the uplink pilot, flexible allocation can be performed according to actual channel conditions (such as CQI) on the premise of ensuring that the total transmission power does not exceed a predetermined total transmission power upper limit.

In the scheme, for the downlink channel, because the power of the uplink pilot frequency is known to be constant, the second communication device can acquire the actual uplink pilot frequency condition, and the first premise is provided for ensuring the correctness of the uplink channel. For a downlink channel, because the downlink pilot frequency is subjected to power adjustment at the first communication device, the estimated downlink channel and the real channel have a difference of a scale factor; however, since the second communication device acquires the downlink channel parameters and processes the transmitted signals to perform some beneficial corrections on the channel, and since the power of the signals is kept unchanged before and after the signals pass through the preprocessing module, the second communication device does not actually need to know the scale factor of the difference between the estimated downlink channel and the actual downlink channel, and only needs to normalize the estimation result, and thus the second communication device can be used for designing the preprocessing module to perform corresponding preprocessing such as pre-equalization or pre-coding.

It can be seen that if the power allocation scheme described in scheme two is adopted, the first communication device does not need to feed back any power allocation information, and therefore, the scheme two can further save feedback overhead relative to the scheme one.

Step 203: the second communication device receives the mixed pilot sent by the first communication device.

The second communication device receives the signal. Extracting the mixed pilot frequency from the pilot frequency, and setting the length of the signal transmitted by the first communication equipment after time delay expansion to be L_ulThe uplink channel arrives at the second communication device, and at the second communication device, the received mixed pilot signal may be represented as:

y_Bp(n)＝diag(Y_up(n)+P(n))F_upH_ul+w_Bp(n)(4)，

wherein y is_BP(n) represents: the second communication device receives the mixed pilot frequency; y is_up(n) represents: the sum of the downlink pilot frequency received by the first communication equipment and the additive noise of the uplink channel passed by the downlink pilot frequency on the frequency domain; p_ul(n) represents: the sum of the uplink pilot frequency sent by the first communication equipment and the additive noise of the uplink channel passing through the uplink pilot frequency on the frequency domain; diag (Y)_up(n)+P_ul(n)) represents: y is_up(n) and P_ul(n) a diagonal matrix of sums, F_upRepresents: a matrix formed by parts corresponding to pilot frequencies in a Discrete Fourier Transform (DFT) matrix of an uplink channel; h_ulRepresents: a convolution matrix for the uplink channel; w is a_Bp(n) represents: additive noise superimposed at the receiving end when the mixed pilot reaches the second communication device.

The function (4) can also be written as a convolution of the time domain signal as shown in the function (5):

<math> <mrow> <msub> <mi>y</mi> <mi>Bp</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>h</mi> <mi>dl</mi> </msub> <mo>*</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mi>w</mi> <mi>Up</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>w</mi> <mi>Bp</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math> (5)，

<math> <mrow> <mo>=</mo> <msub> <mi>h</mi> <mi>dl</mi> </msub> <mo>*</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <mi>w</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math>

wherein h is_dlRepresents: the time domain form of the downlink channel; h is_ulRepresents: the time domain form of the uplink channel;represents: the time domain form of the uplink pilot frequency in the mixed pilot frequency received by the second communication equipment;

represents: the time domain form of the uplink pilot frequency in the mixed pilot frequency received by the second communication equipment; w is a_Up(n) represents: the time domain form of additive noise superimposed by the mixed pilot frequency in the process of passing through the uplink channel; w is a_Bp(n) represents: the pilot signal is in a time domain form of additive noise superposed at a receiving end of the second communication equipment; w (n) represents: a total equivalent noise term;

step 204: and the second communication equipment estimates the uplink channel according to the received mixed pilot frequency and the known uplink pilot frequency to acquire the uplink channel parameters.

After receiving the mixed pilot sent by the first communication device, the second communication device estimates the uplink channel, and specifically, the received mixed pilot may be point-multiplied by an uplink pilot known to the second communication device (the uplink pilot is determined by the second communication device and the first communication device in a communication system through negotiation in advance). I.e. corresponding to the use of the known time-domain form of the uplink pilot in the time domain

Conjugation of (a):

with the received mixed pilot signal y_Bp(n) performing convolution with:

<math> <mrow> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>y</mi> <mi>Bp</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math> (6)，

<math> <mrow> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>h</mi> <mi>dl</mi> </msub> <mo>*</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <msup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> </msup> <mi>w</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math>

without loss of generality, by making a in the functional formula (2) equal to 1, and substituting the functional formulas (2) and (3) into the functional formula (6), respectively, the functional formula (7) can be obtained:

<math> <mrow> <msub> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> </msub> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>y</mi> <mi>Bp</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>+</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <mi>w</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>7</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

the estimation value of the uplink channel parameter can be calculated and obtained according to the function formula (7)

It should be noted that, if the first communication device is transmitting the hybrid pilot and adopts the power allocation scheme of the transmission power allocation in step 202, the second communication device receives the hybrid pilot and uses the received power allocation factor α according to the received power allocation factor αSubstitution of the functions in equations (6) and (7)

Corresponding uplink channel estimation can be carried out according to the replaced functional formula; if the first communication device is transmitting the hybrid pilot by using the power allocation described in the second allocation scheme of the transmission power in step 202, the functions (6) and (7) may be directly applied for calculation.

Step 205: and the second communication equipment estimates the closed-loop channel according to the known downlink pilot frequency and the received mixed pilot frequency to acquire closed-loop channel parameters.

The downlink pilot frequency is from the second communication equipment to the first communication equipment through the downlink channel, and then is returned to the second communication equipment through the uplink channel by the first communication equipment, and passes through a closed-loop channel formed by the uplink channel and the downlink channel.

Therefore, the second communication device can perform closed-loop channel estimation by dot-multiplying the received mixed pilot on the frequency domain by the known downlink pilot (i.e., the downlink pilot sent from the second communication device to the first communication device), similarly to the uplink channel estimation. I.e. corresponding to the time-domain conjugation with the known time-domain form of the downlink pilot

With the received mixed pilot signal y_Bp(n) performing convolution with:

<math> <mrow> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>y</mi> <mi>Bp</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math> (8)，

<math> <mrow> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>h</mi> <mi>dl</mi> </msub> <mo>*</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> </msub> <msup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> </msup> <mi>w</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math>

by substituting functional formula (1) into functional formula (8), functional formula (9) can be obtained:

<math> <mrow> <msub> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>all</mi> </msub> <mo>=</mo> <msub> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>dl</mi> </msub> <mo>*</mo> <msub> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> </msub> <mo>=</mo> <msup> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> </msub> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>y</mi> <mi>bp</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>dl</mi> </msub> <mo>*</mo> <msub> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> </msub> <mo>+</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <mi>w</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>9</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

the estimated value of the closed-loop channel parameter can be calculated and obtained according to the function formula (9)

It should be noted that, if the first communication device is transmitting the hybrid pilot, and the power allocation of the first transmission power allocation scheme between the downlink pilot and the uplink pilot in step 202 is adopted, correspondingly, after the second communication device receives the hybrid pilot, according to the received power, the second communication device receives the hybrid pilotDistribution factor alpha, use of

In alternative functional formulae (8), (9)

Namely, the closed-loop channel can be estimated according to the replaced functional expression; if the first communication device uses the power allocation described in the second allocation scheme of the transmission power between the downlink pilot frequency and the uplink pilot frequency in step 202 when transmitting the hybrid pilot frequency, the closed-loop channel can be estimated by directly applying the functional expressions (8) and (9) to perform calculation.

Step 206: and the second communication equipment acquires the downlink channel parameters according to the closed-loop channel parameters and the uplink channel parameters.

The estimation value of the downlink channel can be obtained by deconvolution operation according to the estimation value of the uplink channel calculated by the functional formula (7) and the estimation value of the closed-loop channel calculated by the functional formula (9)

Obtaining downlink channel parameters

In addition, the downlink channel parameters may also be obtained from the frequency domain, assuming a certain downlink pilot p_iIn the mth sub-channel H in the downlink channel_mAfter being superposed with the uplink pilot frequency at the first communication equipment, the nth subchannel H from the uplink_nReturning to the second communication device, there is a frequency domain representation of functional equations (7), (9):

wherein

To represent: a frequency domain representation of a downlink channel parameter;

a frequency domain representation representing closed-loop channel parameters;represents: frequency domain representation of uplink channel parameters.

It should be noted that, the second communication device in this embodiment may be, but is not limited to, a base station, and the first communication device may be, but is not limited to, a terminal.

As can be seen from the above, the first communication device applying the technical solution of this embodiment sends, to the second communication device, a mixed pilot formed by superimposing the received downlink pilot sent by the first communication device and the uplink pilot that the first communication device needs to send to the second communication device, and the second communication device can estimate the uplink channel according to the mixed pilot and the predicted uplink pilot; according to the mixed pilot frequency and the known downlink pilot frequency, a closed-loop channel can be estimated, and then the downlink channel is estimated by combining the estimated uplink pilot frequency and the estimated closed-loop pilot frequency. The method and the device achieve the purpose that the parameters of the downlink channel can be acquired while the uplink channel is estimated, and compared with the prior art, the signaling overhead for enabling the second communication device to acquire the parameters of the downlink channel is greatly reduced. For example: if the first power allocation scheme in step 202 is adopted, only few signaling transmission power allocation factors are needed to apply the method of the embodiment of the present invention, and if the second power allocation scheme in step 202 is adopted, the signaling overhead required by applying the method of the embodiment of the present invention is zero.

Example 2:

in this embodiment, taking the method for acquiring channel information provided by the embodiment of the present invention applied in the MIMO system as an example, the method is specifically described, and a basic flow of the method is shown in fig. 3, as shown in the figure, the method may include:

step 301: and the second communication equipment transmits the downlink pilot frequency to the first communication equipment.

This step is the same as step 201 in embodiment 1, but since a multi-antenna transmission/reception technique is adopted in the MIMO system, the present embodiment differs from embodiment 1 in that: and each antenna of the second communication equipment respectively issues downlink pilot frequency to the first communication equipment.

In order to make each downlink pilot in the mixed pilots in the technical solution of this embodiment not affect the estimation of each uplink channel and closed-loop channel by the second communication device, each uplink pilot and each downlink pilot between the first communication device and the second communication device may be preset, so that each uplink pilot and each downlink pilot respectively satisfy the following conditions:

(1) for the downlink pilot frequency sent by each antenna of the second communication device to the first communication device, the time delay expansion length L of the convolution result of each downlink pilot frequency in the time domain on the uplink channel can be made_ulDelay spread length L with downlink channel_dlThe sum range is an impulse function, that is, the autocorrelation function of each downlink pilot frequency in the time domain can be represented as:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> <mo>+</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>11</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

wherein p is_dl ^i*(t) represents: downlink pilot frequency p sent by antenna i of second communication equipment to first communication equipment_dl ⁱ(t) conjugation; p is a radical of_dl ^j(n-t) represents: the downlink pilot frequency sent by the antenna j of the second communication device to the first communication device, a is a real number greater than zero, and a can be equal to 1 without loss of generality.

(2) For the uplink pilot frequency of each antenna pair, the convolution result in the time domain of each uplink pilot frequency is the delay spread length L of the uplink channel_ulWithin the range, the impulse function is obtained, that is, the autocorrelation function of each uplink pilot frequency in the time domain can be represented as:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>16</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

wherein i is the identification of the antenna of the first communication device, and j is the identification of the antenna of the first communication device; p is a radical of_ul ^i*(t) represents: uplink pilot p_ul ⁱ(t) conjugation; a is a real number greater than zero, and a can be made equal to 1 without loss of generality.

(3) For each uplink pilot frequency and downlink pilot frequency, the time delay expansion length L of the convolution result of any uplink pilot frequency and any downlink pilot frequency in an uplink channel_ulDelay spread length L with downlink channel_dlThe sum of which is zero. Namely:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0,0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> <mo>+</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>17</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

wherein p is_ul ^i*(t) represents: uplink pilot frequency p transmitted by first communication equipment antenna i to second communication equipment_ul ⁱ(t) conjugation; p is a radical of_ul ^j(t) represents: an uplink pilot frequency transmitted by a first communication equipment antenna j to second communication equipment; i. j is the antenna id, i may be equal to j, a is a real number greater than zero, and a may be equal to 1 without loss of generality.

The second communication device sends the downlink pilot frequency meeting the limiting conditions represented by the functional expressions (11) and (17) to the first communication device, so that the second communication device directly superimposes the received downlink pilot frequency and the received uplink pilot frequency after receiving the downlink pilot frequency without performing additional processing on the received downlink pilot frequency.

Step 302: the first communication equipment receives the downlink pilot frequency, superposes the received downlink pilot frequency and the uplink pilot frequency to generate a mixed pilot frequency, and sends the superposed mixed pilot frequency to the second communication equipment.

It is assumed that in the MIMO system of this embodiment, the second communication device and the second communication system both adopt 2 antennas for transceiving, the second communication device issues downlink pilot to the first communication device through the antennas 1 and 2, respectively, and at the first communication device, the pilot signal y received by the antenna 1 of the first communication device is_uP ¹(n) is:

$y_{\mathrm{uP}}^1\left(n\right)=\mathrm{diag}\left(P_{\mathrm{dl}}^1\left(n\right)\right)F_{\mathrm{dp}}{h}_{\mathrm{dl}}^{11}+\mathrm{diag}\left(P_{\mathrm{dl}}^2\left(n\right)\right)F_{\mathrm{dp}}{h}_{\mathrm{dl}}^{12}+w_{\mathrm{Up}}^1\left(n\right)---\left(12\right),$

wherein P is_dl ¹(n) represents: a downlink pilot frequency received by an antenna 1 of first communication equipment and transmitted by an antenna 1 of second communication equipment; p_dl ²(n) represents: a downlink pilot frequency received by an antenna 1 of first communication equipment and transmitted by an antenna 2 of second communication equipment; h is_dl ¹¹Represents: a downlink channel from the antenna 1 of the second communication device to the antenna 1 of the first communication device; h is_dl ¹²Represents: a downlink channel from the antenna 2 of the second communication device to the antenna 1 of the first communication device; f_dpRepresents: and for the DFT matrix of the downlink channel, a matrix is formed by the parts corresponding to the pilot frequency.

The pilot signal y received by the antenna 2 of the first communication device_uP ²(n) is:

$y_{\mathrm{uP}}^2\left(n\right)=\mathrm{diag}\left(P_{\mathrm{dl}}^1\left(n\right)\right)F_{\mathrm{dp}}{h}_{\mathrm{dl}}^{21}+\mathrm{diag}\left(P_{\mathrm{dl}}^2\left(n\right)\right)F_{\mathrm{dp}}{h}_{\mathrm{dl}}^{22}+w_{\mathrm{Up}}^1\left(n\right)---\left(13\right),$

wherein P is_dl ¹(n) represents: a downlink pilot frequency received by an antenna 2 of first communication equipment and transmitted by an antenna 1 of second communication equipment; p_dl ²(n) represents: the antenna 2 of the first communication device receives the downlink pilot frequency transmitted by the antenna 2 of the second communication device; h is_dl ²¹Represents: a downlink channel from an antenna 1 of the second communication device to an antenna 2 of the first communication device; h is_dl ²²Represents: a downlink channel from the antenna 2 of the second communication device to the antenna 2 of the first communication device; f_dpRepresents: and for the DFT matrix of the downlink channel, a matrix is formed by the parts corresponding to the pilot frequency.

At a first communication device, a first communicationAfter the received signal is demodulated by CP and OFDM, the down pilot signal on the pilot channel corresponding to each receiving antenna is extracted and superposed with the up pilot to be sent of the antenna correspondingly to generate the mixed pilot to be sent of each antenna on the first communication equipment. For example: hybrid pilot x on antenna 1 of a first communication device₁(n) is:

$x_1\left(n\right)=y_{\mathrm{up}}^1\left(n\right)+P_{\mathrm{ul}}^1\left(n\right)---\left(14\right),$

wherein P is_ul ¹(n) represents: and the antenna 1 of the first communication device transmits the uplink pilot frequency to the second communication device. The mixed pilot on antenna 2 of the first communication device is:

$x_2\left(n\right)=y_{\mathrm{up}}^2\left(n\right)+P_{\mathrm{ul}}^2\left(n\right)---\left(15\right).$

wherein P is_ul ²(n) represents: and the antenna 2 of the first communication device transmits the uplink pilot frequency to the second communication device.

The uplink pilot transmitted from the first communication device to the second communication device satisfies the constraint conditions represented by functional expressions (16) and (17) in step 301.

The first communication equipment carries out OFDM modulation on the mixed pilot frequency of each antenna on the uplink data, and the mixed pilot frequency is added with the CP and then transmitted to the second communication equipment through an uplink channel.

The first communication system may refer to the first and second power allocation schemes in embodiment 1, and adopt the following power allocation schemes:

the third scheme is as follows: total power constant scheme

The same as in step 202 of example 1 is: when the total transmission power of the pilot subcarriers of the first communication device (including the power for transmitting the uplink pilot and the downlink pilot in the subcarriers) is agreed to be constant, the second communication device may be notified of the constant value after the agreement.

The difference from the first embodiment is that: since the current system is a MIMO system, downlink pilots received by each antenna of the first communication device may come from different antennas of the second communication device, and therefore, a mixed pilot transmitted by each antenna of the first communication device includes at least a plurality of uplink pilots, where the mixed pilot is: and superposing the plurality of downlink pilot frequencies and the uplink pilot frequency which is required to be transmitted by the antenna to the second communication equipment. Therefore, there are multiple power allocation factors, and the ratio of the power allocated to each downlink pilot or uplink pilot to the total power.

And the scheme is as follows: uplink pilot power constancy scheme

The difference between this scheme and the first scheme in step 202 of embodiment 1 is that the first communication device uses multiple antennas for transmission, and each antenna transmits its own uplink pilot, so that there may be more than one uplink pilot transmitted by the first communication device, and therefore, for the power of the uplink pilot allocated to each antenna pair, it may be negotiated to make the transmission power of the uplink pilot of the first communication device antenna be a constant value, and after the negotiation, the constant value of each uplink pilot power is notified to the second communication device.

For the power of the uplink pilot of each antenna, similar to the second scheme in embodiment 1, the power can be flexibly allocated according to the channel condition (e.g. CQI) on the premise that the total transmit power does not exceed the predetermined total transmit power upper limit.

It can be seen that if the power scheme described in scheme four is applied, the first communication device does not need to feed back any power allocation information, which can further save feedback overhead with respect to scheme three.

Step 303: the second communication device receives the mixed pilot transmitted by the first communication device.

The mixed pilot frequency sent by the first communication equipment reaches the second communication equipment after passing through an uplink channel. Assuming that the second communication device employs 2-antenna transceiving, at the second communication device, the hybrid pilot received by the antenna 1 of the second communication device is a superposition of the hybrid pilots transmitted by the antennas 1 and 2 of the second communication terminal, and the hybrid pilot received by the antenna 1 of the second communication device may be represented as:

$y_{\mathrm{BP}}^1\left(n\right)=\mathrm{diag}(Y_{\mathrm{up}}^1\left(n\right)+P_{\mathrm{ul}}^1\left(n\right))F_{\mathrm{up}}{h}_{\mathrm{ul}}^{11}+\mathrm{diag}(Y_{\mathrm{up}}^2\left(n\right)+P_{\mathrm{ul}}^2\left(n\right))F_{\mathrm{up}}{h}_{\mathrm{ul}}^{12}+w_{\mathrm{Bp}}^1\left(n\right)---\left(18\right),$

wherein h is_ul ¹¹Represents: an uplink channel from antenna 1 of the first communication device to antenna 1 of the second communication device; h is_ul ¹²Represents: an uplink channel from antenna 2 of the first communication device to antenna 1 of the second communication device; w is a_Bp ¹(n) represents: additive noise superimposed by the signal at the antenna 1 of the second communication device; f_upRepresents: and a matrix formed by parts corresponding to the pilot frequency in the DFT matrix of the uplink channel.

Similarly, the hybrid pilot received by antenna 2 of the second communication device can be expressed as:

$y_{\mathrm{BP}}^2\left(n\right)=\mathrm{diag}(Y_{\mathrm{up}}^1\left(n\right)+P_{\mathrm{ul}}^1\left(n\right))F_{\mathrm{up}}{h}_{\mathrm{ul}}^{21}+\mathrm{diag}(Y_{\mathrm{up}}^2\left(n\right)+P_{\mathrm{ul}}^2\left(n\right))F_{\mathrm{up}}{h}_{\mathrm{ul}}^{22}+w_{\mathrm{Bp}}^2\left(n\right)---\left(19\right),$

wherein h is_ul ²¹Represents: an uplink channel from antenna 1 of the first communication device to antenna 2 of the second communication device; h is_ul ²²Represents: an uplink channel from antenna 2 of the first communication device to antenna 2 of the second communication device; w is a_Bp ²(n) represents:additive noise superimposed on the signal at the antenna 2 of the second communication device.

In the present embodiment, the first communication device and the second communication system both transmit and receive using 2 antennas, but the present invention is not limited thereto, and the number of the transmitting and receiving antennas of the first communication device and the second communication system may be different.

Step 304: and the second communication equipment estimates each uplink channel according to the received mixed pilot frequency and each known uplink pilot frequency to acquire each uplink channel parameter.

For each uplink channel estimate, the second communication device dot-multiplies the mixed pilot received by each antenna on the frequency domain using the known each uplink pilot. I.e. the time domain form corresponding to the uplink pilot of the antenna i of the first communication device known to the second communication device in the time domain

Conjugation of (2)

Mixed pilot signal y received with antenna j of the second communication device_BP ^j(n) performing convolution to estimate an uplink channel from antenna i to antenna j,

and y_BP ^j(n) performing the convolution may be expressed as:

<math> <mrow> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>1</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>y</mi> <mi>Bp</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math>

<math> <mrow> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>1</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <mo>[</mo> <msubsup> <mi>h</mi> <mi>dl</mi> <mn>11</mn> </msubsup> <mo>*</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>11</mn> </msubsup> <mo>*</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msubsup> <mi>h</mi> <mi>dl</mi> <mn>12</mn> </msubsup> <mo>*</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>11</mn> </msubsup> <mo>*</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msubsup> <mi>h</mi> <mi>dl</mi> <mn>21</mn> </msubsup> <mo>*</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>12</mn> </msubsup> <mo>*</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math> (20)。

<math> <mrow> <mo>+</mo> <msubsup> <mi>h</mi> <mi>dl</mi> <mn>22</mn> </msubsup> <mo>*</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>12</mn> </msubsup> <mo>*</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>11</mn> </msubsup> <mo>*</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>12</mn> </msubsup> <mo>*</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msubsup> <mi>w</mi> <mi>Bp</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>]</mo> </mrow> </math>

by substituting functional expressions (16) and (17) into functional expression (20), the uplink channel from the antenna i of the first communication device to the antenna j of the second communication device can be estimated

<math> <mrow> <msubsup> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> <mi>ij</mi> </msubsup> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mi>i</mi> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>y</mi> <mi>Bp</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mi>ij</mi> </msubsup> <mo>+</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mi>i</mi> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>w</mi> <mi>Bp</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>21</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow> </math>

For example: for the estimation of the uplink channel from the antenna 1 of the first communication device to the antenna 1 of the second communication device, the second communication device uses the known uplink pilot of the antenna 1 of the first communication device (known in advance)

And the signal y received by the antenna 1 of the second communication device_BP ¹(n) convolution is carried out, and an uplink channel h can be estimated_ul ¹¹：

<math> <mrow> <msubsup> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> <mn>11</mn> </msubsup> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>1</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>y</mi> <mi>Bp</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>11</mn> </msubsup> <mo>+</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>1</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>w</mi> <mi>Bp</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>22</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

Similarly, the second communication device uses the known uplink pilot of the antenna 2 of the first communication device (predetermined and known)

And the signal y received by the antenna 1 of the second communication device_BP ¹(n) convolution is carried out, and an uplink channel h can be estimated_ul ¹²：

<math> <mrow> <msubsup> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> <mn>12</mn> </msubsup> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>2</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>y</mi> <mi>Bp</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>12</mn> </msubsup> <mo>+</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>2</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>w</mi> <mi>Bp</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>23</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

Similarly, the second communication device uses the known uplink pilot of the antenna 1 of the first communication device (predetermined and known)

And the signal y received by the antenna 2 of the second communication device_BP ²(n) convolution is carried out, and an uplink channel h can be estimated_ul ²¹：

<math> <mrow> <msubsup> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> <mn>22</mn> </msubsup> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>1</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>y</mi> <mi>Bp</mi> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>21</mn> </msubsup> <mo>+</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>1</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>w</mi> <mi>Bp</mi> <mn>2</mn> </msubsup> <mi>n</mi> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>24</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow> </math>

Similarly, the second communication device uses the known uplink pilot of the antenna 2 of the first communication device (predetermined and known)And the signal y received by the antenna 2 of the second communication device_BP ²(n) convolution is carried out, and an uplink channel h can be estimated_ul ²²：

<math> <mrow> <msubsup> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> <mn>22</mn> </msubsup> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>2</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>y</mi> <mi>Bp</mi> <mn>2</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msubsup> <mi>h</mi> <mi>ul</mi> <mn>22</mn> </msubsup> <mo>+</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mrow> <mo>*</mo> <mn>2</mn> </mrow> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msubsup> <mi>w</mi> <mi>Bp</mi> <mn>1</mn> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>25</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow> </math>

It should be noted that, if the first communication device uses the power allocation described in the third scheme in step 301 when transmitting the hybrid pilot, then correspondingly, after receiving the hybrid pilot, the second communication device, according to the known ratio of the uplink pilot power to the total power: distribution factor alpha, use of

Corresponding substitution in function (21)

Namely, each uplink channel can be estimated according to the replaced functional formula; if the first communication device uses the power allocation of the transmission power allocation scheme four of the downlink pilot frequency and the uplink pilot frequency in step 301 when transmitting the hybrid pilot frequency, the functional formula (21) may be directly applied to calculate and estimate each uplink channel.

Step 305: and the second communication equipment estimates each closed-loop channel according to the known downlink pilot frequency and the received mixed pilot frequency to acquire each closed-loop channel parameter.

Each downlink pilot frequency is from the second communication equipment to the first communication equipment through the downlink channel, and then is returned to the second communication equipment through the uplink channel by the first communication equipment, and passes through a closed-loop channel formed by the uplink channel and the downlink channel.

Therefore, the second communication device can perform convolution in the time domain or dot product in the frequency domain on the downlink pilot frequency sent by each antenna of the known communication device and the mixed pilot frequency received by the second communication device, respectively, similarly to the uplink channel estimation in step 302. For example:

in the time domain, the time domain form of the downlink pilot frequency sent to the first communication equipment by the antenna i of the second communication equipment known by the second communication equipmentConjugation of (2)

Respectively with the mixed pilot signal y received by the second communication device_BPAnd (n) carrying out convolution operation, carrying out equation solution on each convolution operation expression, and estimating each closed-loop channel to obtain each closed-loop channel parameter.

For example: taking the case that the second communication device transmits and receives data by 2 antennas as an example, for the mixed pilot received by the antenna 1 of the second communication device, the downlink pilot of the antenna 1 and the downlink pilot of the antenna 2 may be used to perform convolution in the time domain or dot product operation in the frequency domain on the mixed pilot respectively; for the mixed pilot received by the antenna 2 of the second communication device, the mixed pilot may be convolved in the time domain or dot-multiplied in the frequency domain by using the downlink pilot of the antenna 1 and the downlink pilot of the antenna 2, respectively, in the same manner. And then, the estimation result of the closed-loop channel can be obtained by combining each operation function expression.

Step 306: and the second communication equipment acquires each downlink channel parameter according to each closed-loop channel parameter and each uplink channel parameter.

Similar to step 206 in embodiment 1, the downlink channel parameters of the antenna pair are obtained according to the closed-loop channel parameters and the uplink channel parameters. For example:

the downlink channel is a 2 x 2 matrix H_DUplink messageMatrix H with 2 x 2 lanes_UWherein:

$H_D=\left[\begin{array}{cc}{h}_d^1& h_d^2\\ h_d^3& h_d^4\end{array}\right]---\left(26\right),$

$H_U=\left[\begin{array}{cc}{h}_u^1& h_u^2\\ h_u^3& h_u^4\end{array}\right]---\left(27\right)$

the closed-loop channel can be expressed as: h ═ H_D·H_UNamely, the following steps are provided:

$H=\left[\begin{array}{cc}{h}_d^1{h}_u^1+h_d^2{h}_u^3& h_d^1{h}_u^2+h_d^2{h}_u^4\\ h_d^3{h}_u^1+h_d^4{h}_u^3& h_d^3{h}_u^2+h_d^4{h}_u^4\end{array}\right]---\left(28\right),$

as can be seen from the functional expression (28), the closed-loop channel H and each uplink channel H are estimated from the estimated closed-loop channel H_u ¹、h_u ²、h_u ³、h_u ⁴Can obtain each downlink channel h_d ¹、h_d ²、h_d ³、h_d ⁴。

It should be noted that, the second communication device in this embodiment may be, but is not limited to, a base station, and the first communication device may be, but is not limited to, a terminal.

It will be understood by those skilled in the art that all or part of the steps in the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, where the program may be stored in a computer-readable storage medium, and when executed, the program may include the following steps: the second communication equipment receives the downlink pilot frequency sent by the first communication equipment, superposes the received downlink pilot frequency and the uplink pilot frequency to generate a mixed pilot frequency, and sends the mixed pilot frequency to the first communication equipment; the first communication equipment receives the mixed pilot frequency, estimates an uplink channel according to the received mixed pilot frequency and the known uplink pilot frequency, and acquires uplink channel parameters; the first communication equipment estimates a closed-loop channel according to the known downlink pilot frequency and the received mixed pilot frequency to acquire closed-loop channel parameters; and the first communication equipment acquires the downlink channel parameters according to the closed-loop channel parameters and the uplink channel parameters. The storage medium referred to herein is, for example: ROM/RAM, magnetic disk, optical disk, etc.

As can be seen from the above, after receiving downlink pilot frequencies issued by each antenna of the second communication device, when each antenna sends uplink pilot frequencies, each antenna of the first communication device applying the technical solution of this embodiment sends mixed pilot frequencies, which are formed by superimposing all downlink pilot frequencies received by the antenna and uplink pilot frequencies to be sent by the antenna, to the second communication device, and the second communication device can estimate each uplink channel according to the mixed pilot frequencies and known uplink pilot frequencies; in addition, the second communication device may further estimate each closed-loop channel according to the mixed pilot and the known downlink pilots, and then estimate each downlink channel by combining the estimation of each uplink pilot and each closed-loop pilot. The method and the device can achieve the purpose that parameters of each downlink channel can be obtained while each uplink channel is estimated, and meanwhile compared with the prior art, the technical scheme of the embodiment greatly reduces signaling overhead for obtaining the parameters of the downlink channel. For example:

if the power allocation scheme three in step 302 is utilized, only very little signaling overhead is required for transmitting the power allocation factor, whereas if the power allocation scheme four in step 302 is referred to, the required signaling overhead is zero.

Example 3:

in this embodiment, another method for acquiring channel information provided by the embodiment of the present invention is applied in a SISO system as an example, and the method is specifically described, fig. 4 is a schematic flowchart of the method of this embodiment, and as shown in fig. 4, the method may include:

step 401: and the second communication equipment transmits the downlink pilot frequency to the first communication equipment.

This step is basically the same as step 201 in embodiment 1, except that:

in order to prevent the downlink pilot in the mixed pilot in the technical solution of the present invention from affecting the estimation of the uplink channel by the first communication device, the uplink pilot and the downlink pilot between the first communication device and the second communication device may be preset, so that the uplink pilot and the downlink pilot respectively satisfy the following conditions:

(1) for the downlink pilot frequency sent by the second communication device to the first communication device, the time delay expansion length L of the convolution result of the sent downlink pilot frequency in the time domain on the uplink channel can be made_ulThe range of (2) is an impulse function, that is, the autocorrelation function of the downlink pilot frequency in the time domain can be represented as:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msubsup> <mi>p</mi> <mi>dl</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msub> <mi>p</mi> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>29</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

wherein p is_dl ^*(t) represents: downlink pilot

Conjugation of (1); l is_dlRepresents: the delay spread length of the downlink channel; a is a real number greater than zero, and a may be equal to 1 without loss of generality.

(2) For the uplink pilot frequency transmitted from the first communication device to the second communication device, the convolution result in the time domain of the uplink pilot frequency is the delay spread length L of the uplink channel_ulWithin the range is an impulse function. That is, the autocorrelation function of the uplink pilot in the time domain can be expressed as shown in the functional formula (2) in step 201 of embodiment 1.

(3) For the uplink pilot frequency and the downlink pilot frequency, the convolution result of the uplink pilot frequency and the downlink pilot frequency has the delay expansion length L of the uplink channel_ulIs zero in the range of (1). Namely:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msubsup> <mi>p</mi> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msub> <mi>p</mi> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0,0</mn> <mo>&le;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>30</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

it should be noted that if the downlink pilot frequency satisfies the condition represented by the function (3) in embodiment 1, it inevitably satisfies the condition represented by the function (30) in this embodiment, that is to say: the condition restricted by the functional expression (30) is a subset of the condition restricted by the functional expression (3).

The second communication device sends the downlink pilot frequency meeting the limitation of the functional expressions (29) and (30) to the first communication device, so that the second communication device directly superposes the received downlink pilot frequency and the uplink pilot frequency after receiving the downlink pilot frequency without performing additional processing on the received downlink pilot frequency.

Step 402: the first communication equipment receives the downlink pilot frequency, superposes the received downlink pilot frequency and the uplink pilot frequency to generate a mixed pilot frequency, and sends the superposed mixed pilot frequency to the second communication equipment.

This step is basically the same as step 202 in embodiment 1: after receiving the downlink pilot frequency, the first communication device superimposes the received downlink pilot frequency and the uplink pilot frequency to be sent to generate a mixed pilot frequency, and sends the mixed pilot frequency to the second communication device. The difference between this step and step 202 is that the uplink pilot transmitted from the first communication device to the second communication device satisfies the constraint conditions expressed by the functional expressions (2) and (30) in step 401.

After the first communication equipment generates the mixed pilot frequency, when uplink data are transmitted to the second communication equipment, the superposed mixed pilot frequency and the uplink data are subjected to OFDM modulation, and uplink transmission is carried out after CP is added, and the mixed pilot frequency is transmitted to the second communication equipment.

The first communication device may use the pilot power allocation scheme described in scheme one or scheme two in embodiment 1 when transmitting the hybrid pilot, which is described in detail in relation to embodiment 1. And will not be described in detail herein.

Step 403: the second communication device receives the mixed pilot sent by the first communication device.

This step is the same as step 203 in example 1.

The length of the delay spread of the mixed pilot frequency sent by the first communication equipment is set to be L_ulAfter reaching the second communication device, the hybrid pilot received at the second communication device may be represented in the form shown by the functional formula (2) in step 201 of embodiment 1.

Step 404: and the second communication equipment estimates the uplink channel according to the received mixed pilot frequency and the known uplink pilot frequency to acquire the uplink channel parameters.

Similar to step 204 in embodiment 1, the second communication device uses the known conjugate of the time domain form of the uplink pilot in the time domainWith the received mixed pilot signal y_Bp(n) convolving to obtain a functional expression (6), and estimating the uplink pilot frequency according to the functional expression (6):

<math> <mrow> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>y</mi> <mi>Bp</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math> (6)，

<math> <mrow> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>h</mi> <mi>dl</mi> </msub> <mo>*</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>dl</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>*</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>+</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <mi>w</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> </mrow> </math>

functional formula (7) can be obtained by substituting functional formulas (2) and (30) into functional formula (6) with a in functional formula (2) equal to 1:

<math> <mrow> <msub> <mover> <mi>h</mi> <mo>^</mo> </mover> <mi>ul</mi> </msub> <mo>=</mo> <msubsup> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <msub> <mi>y</mi> <mi>Bp</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mi>h</mi> <mi>ul</mi> </msub> <mo>+</mo> <msub> <mover> <mi>p</mi> <mo>&RightArrow;</mo> </mover> <mi>ul</mi> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>*</mo> <mi>w</mi> <mrow> <mo>(</mo> <mi>n</mi> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>7</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

the estimation value of the uplink channel parameter can be calculated and obtained according to the function formula (7)

It should be noted that, if the first communication device adopts the power allocation scheme described in the first scheme in step 202 when transmitting the hybrid pilot, the second communication device receives the hybrid pilot and uses the received power allocation factor α according to the received power allocation factor α

Substitution of the functions in equations (6) and (7)

The estimation value of the uplink channel can be calculated and obtained according to the replaced functional formula; if the first communication device uses the power allocation in step 202 according to scheme two, the first communication device calculates the estimated value of the uplink channel by directly applying functions (6) and (7).

Step 405: and the second communication equipment recovers and acquires the mixed pilot frequency transmitted by the first communication equipment according to the uplink channel parameters.

According to the estimation result of the uplink channel, the mixed pilot frequency y received by the second communication equipment can be used_BpAnd (n) carrying out equalization processing to recover and acquire the signal of the mixed pilot frequency at the transmitting end (the first communication device). Examples of ways in which equalization may be restoredSuch as: ZF equalization, MMSE equalization, etc., using ZF equalization, for example, can result in:

${\hat{y}}_{\mathrm{ue}}\left(n\right)={\left(\mathrm{diag}\left({\hat{H}}_{\mathrm{ul}}\right)\right)}^{-1}{y}_{\mathrm{Bp}}\left(n\right)---\left(31\right)$

wherein,

represents: recovering the obtained mixed pilot frequency sent by the first communication equipment;

represents: estimating the parameters of the obtained uplink channel;

represents: estimating a diagonal matrix formed by the obtained uplink channel parameters; y is_Bp(n) represents: the mixed pilot received by the second communication device,

represents: to pair

The matrix is the inverse of the matrix.

The signal obtained by the hybrid pilot at the transmitting end (first communication device), that is, the hybrid pilot sent by the first communication device, can be calculated according to function (31).

Step 406: and the second communication equipment estimates and acquires the downlink channel parameters according to the recovered mixed pilot frequency, the known uplink pilot frequency and the known downlink pilot frequency.

In function (31)

Can be expressed in the form of:

${\hat{y}}_{\mathrm{ue}}\left(n\right)={\left(\mathrm{diag}\left({\hat{H}}_{\mathrm{ul}}\right)\right)}^{-1}{y}_{\mathrm{Bp}}\left(n\right)$

$=\mathrm{diag}\left(P_{\mathrm{dl}}\left(n\right)\right)F_{\mathrm{dp}}{h}_{\mathrm{dl}}+w_{\mathrm{up}}\left(n\right)+P_{\mathrm{ul}}\left(n\right)+{\left(\mathrm{diag}\left({\hat{H}}_{\mathrm{ul}}\right)\right)}^{-1}{w}_{\mathrm{Bp}}\left(n\right)---\left(32\right),$

$=\mathrm{diag}\left(P_{\mathrm{dl}}\left(n\right)\right)F_{\mathrm{dp}}{h}_{\mathrm{dl}}+P_{\mathrm{ul}}\left(n\right)+w\left(n\right)$

wherein, P_dl(n) represents: the frequency domain form of the downlink pilot frequency; diag (P)_dl(n)) represents: a diagonal matrix formed by pilots on a downlink frequency domain; f_dpRepresents: an IFFT matrix of an uplink pilot frequency; h is_dlRepresents: a downlink time domain channel vector; w is a_up(n) represents: additive noise superposed on the uplink channel by the mixed pilot frequency; p is a radical of_ul(n) represents: the frequency domain form of the uplink pilot frequency; diag (P)_dl(n)) represents: a diagonal matrix formed by downlink pilot frequency; w is a_Bp(n) represents: superimposed noise on the mixed pilot received by the second communications device; w (n) represents: the total equivalent noise term.

As can be seen from the functional expression (32), the uplink pilot P known to the second communication device is subtracted from this expression_ul(n) (the second communication device has a pre-agreement with the first communication device), the estimated value can be obtained: diag (P)_dl(n))F_dph_dl+w(n)。

After estimation, the estimation value is obtained: diag (P)_dl(n))F_dph_dl+ w (n), then using the known second communication device to send down the downlink pilot P to the first communication device_dl(n), and known as F_dpThe parameter h of the downlink channel can be estimated and obtained_dl。

It should be noted that, the second communication device in this embodiment may be, but is not limited to, a base station, and the first communication device may be, but is not limited to, a terminal.

As can be seen from the above, when the first communication device applying the technical scheme of this embodiment receives the downlink pilot sent by the second communication device and then sends the uplink pilot to the second communication device, the first communication device superimposes the received downlink pilot and the uplink pilot to be sent to generate a mixed pilot, and sends the mixed pilot to the second communication device. After the second communication device receives the mixed pilot frequency, an uplink channel can be estimated according to the mixed pilot frequency and the known uplink pilot frequency; and estimating and acquiring parameters of a downlink channel according to the recovered mixed pilot sent by the first communication device and the known downlink pilot sent by the first communication device to the first communication device and the uplink pilot sent by the first communication device to the first communication device. The method and the device can acquire the parameters of the downlink channel while estimating the uplink channel, and compared with the prior art, the technical scheme of the embodiment greatly reduces the signaling overhead for acquiring the parameters of the downlink channel.

In addition, since it is not necessary to obtain the downlink channel parameters by calculating the closed-loop channel parameters in this embodiment, for the uplink pilot and the downlink pilot, the delay spread length L of the uplink channel of the convolution result between them_ulIs zero (satisfies function (30)), without the delay spread length L in the closed-loop channel as required in embodiment 1_ul+L_dlIs zero (satisfies functional formula (3)). The number of available pilot sequences due to the constraint of function (3) is: N/(L)_ul+L_dl) Where N is the length of the OFDM symbol, and the number of available pilot sequences limited by the function (30) is: N/L_ul. It can be seen that: compared with the technical scheme of embodiment 1, the technical scheme of this embodiment can greatly increase the number of available pilots in the OFDM symbol, so that the pilot overhead is further reduced.

Example 4:

in this embodiment, another method for acquiring channel information provided by the embodiment of the present invention is applied in an MIMO system as an example, and the method is specifically described, where a basic flow of the method is shown in fig. 5, as shown in the figure, the method may include:

step 501: and the second communication equipment transmits the downlink pilot frequency to the first communication equipment.

This step is the same as step 301 in embodiment 2, except that: in order to prevent each downlink pilot in the mixed pilots in the technical solution of the present invention from affecting the estimation of each uplink channel and closed-loop channel by the second communication device, each uplink pilot and each downlink pilot between the first communication device and the second communication device may be preset so that each uplink pilot and each downlink pilot respectively satisfy the following conditions:

(1) for the downlink pilot frequency sent by each antenna of the second communication device to the first communication device, the time delay expansion length L of the convolution result of each downlink pilot frequency in the time domain on the uplink channel can be made_ulThe range of (2) is an impulse function, that is, the autocorrelation function of each downlink pilot frequency in the time domain can be represented as:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>33</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

wherein p is_dl ^i*(t) represents: downlink pilot frequency p issued by antenna i of first communication equipment to second communication equipment_dl ⁱ(t) conjugation; p is a radical of_dl ^j(n-t) represents: an antenna j of first communication equipment transmits downlink pilot frequency to second communication equipment; l is_dlThe time delay expansion length of a downlink channel; i. j is an antenna identification, i may be equal to j; a is a real number greater than zero, and a can be made equal to 1 without loss of generality.

(2) For the downlink pilot frequency sent by each antenna of the second communication equipment to the first communication equipment, the convolution result in the time domain of the downlink pilot frequency is the time delay expansion length L of the uplink channel_ulWithin the range, the impulse function is obtained, that is, the autocorrelation function of each uplink pilot frequency in the time domain can be represented as:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>39</mn> <mo>)</mo> </mrow> <mo>,</mo> </mrow> </math>

wherein, the p is_ul ^i*(t) uplink pilot p sent by antenna i of first communication device to second communication device_ul ⁱConjugation of (t), p_ul ^j(n-t) is an uplink pilot frequency transmitted by the antenna j of the first communication device to the second communication device, L_ulFor the delay spread length of the uplink channel, a is a real number greater than zero, i and j are both antenna identifiers of the second communication device, and i may be equal to j.

(2) For each uplink pilot frequency and downlink pilot frequency, the time delay expansion length L of the convolution result of any uplink pilot frequency and any downlink pilot frequency in an uplink channel_ulIs zero in the range of (1). Namely:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0,0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>34</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow> </math>

the second communication device sends the downlink pilot frequency which meets the limiting conditions represented by the functional expressions (33) and (34) to the first communication device, so that the second communication device directly superposes the received downlink pilot frequency and the received uplink pilot frequency after receiving the downlink pilot frequency without performing additional processing on the received downlink pilot frequency.

Step 502: the first communication equipment receives the downlink pilot frequency, superposes the received downlink pilot frequency and the uplink pilot frequency to generate a mixed pilot frequency, and sends the superposed mixed pilot frequency to the second communication equipment.

This step is basically the same as step 302 in embodiment 2, except that: the uplink pilot transmitted from the first communication device to the second communication device satisfies the constraint conditions represented by the functional expressions (39) and (34) in step 501.

The first communication equipment carries out OFDM modulation on the mixed pilot frequency of each antenna on the uplink data, and the mixed pilot frequency is added with the CP and then transmitted to the second communication equipment through an uplink channel.

In the method of this embodiment, the first communication device may use the mixed pilot of each antenna in the pilot power allocation scheme described in scheme three or scheme four in embodiment 2, which is described in detail in the related description of embodiment 2. And will not be described in detail herein.

Step 503: the second communication device receives the mixed pilot transmitted by the first communication device.

This step is basically the same as step 303 in embodiment 2. Assuming that the MIMO system of this embodiment employs 2-antenna transmission and reception in both the second communication device and the second communication system, the mixed pilot received by the antenna 1 of the second communication device can be expressed in the form shown by the functional formula (18) in the same manner as step 303 in embodiment 2. The mixed pilot received by the antenna 2 of the second communication device can be expressed in the form shown by the functional formula (19).

In the present invention, the second communication device and the second communication system both transmit and receive using 2 antennas, but the present invention is not limited thereto, and the number of the transmitting and receiving antennas of the second communication device and the second communication system may be different.

Step 504: and the second communication equipment estimates each uplink channel according to the received mixed pilot frequency and each known uplink pilot frequency to acquire each uplink channel parameter.

The specific implementation of this step is the same as the specific implementation of step 304 in embodiment 2, and is not described herein again.

Step 505: and the second communication equipment recovers and acquires the mixed pilot frequency transmitted by each antenna of the first communication equipment according to each uplink channel parameter obtained by estimation.

And the second communication equipment performs equalization recovery on the mixed pilot frequency received by each antenna of the base station according to each estimated uplink channel to acquire the signal of the second communication equipment at the transmitting end. Take the example that the second communication device and the second communication system both adopt 2 antennas for transceiving: the mixed pilot received by the antenna 1 of the second communication apparatus can be expressed in the form shown by the functional formula (18), and the mixed pilot received by the antenna 2 of the second communication apparatus can be expressed in the form shown by the functional formula (19). Are respectively paired with y_BP ¹(n)、y_BP ²(n) performing equalization recovery to obtain the hybrid pilot x transmitted by the antenna 1 of the first communication device₁(n), hybrid pilot x transmitted by antenna 2 of the first communication device₂(n) of (a). The equalization method can use ZF equalization, MMSE equalization or the like.

For the sake of facilitating the equalization restoration process, functional expressions (18) and (19) are expressed as follows:

$y_{\mathrm{BP}}^1\left(n\right)=h_{\mathrm{ul}}^{11}{x}_1\left(n\right)+h_{\mathrm{ul}}^{12}{x}_2\left(n\right)---\left(35\right),$

$y_{\mathrm{BP}}^2\left(n\right)=h_{\mathrm{ul}}^{21}{x}_1\left(n\right)+h_{\mathrm{ul}}^{22}{x}_2\left(n\right)---\left(36\right).$

from the functional equations (35), (36), it is possible to obtain:

$\left[\begin{array}{c}{y}_{\mathrm{BP}}^1\left(n\right)\\ y_{\mathrm{BP}}^2\left(n\right)\end{array}\right]=\left[\begin{array}{cc}{h}_{\mathrm{ul}}^{11}& h_{\mathrm{ul}}^{12}\\ h_{\mathrm{ul}}^{21}& h_{\mathrm{ul}}^{22}\end{array}\right]\left[\begin{array}{c}{x}_1\left(n\right)\\ x_2\left(n\right)\end{array}\right]=H\left[\begin{array}{c}{x}_1\left(n\right)\\ x_2\left(n\right)\end{array}\right]---\left(37\right),$

according to function (37), there are:

$\left[\begin{array}{c}{x}_1\left(n\right)\\ x_2\left(n\right)\end{array}\right]=H^{-1}\left[\begin{array}{c}{y}_{\mathrm{BP}}^1\left(n\right)\\ y_{\mathrm{BP}}^2\left(n\right)\end{array}\right]---\left(38\right)$

the mixed pilots transmitted by the first communication device antennas 1, 2 are estimated and obtained according to the function (38): x is the number of₁(n)、x₂(n)。

Step 506: and the second communication equipment estimates and acquires each downlink channel parameter according to the recovered mixed pilot frequency, the known uplink pilot frequency and the known downlink pilot frequency.

To obtain x₁(n) and x₂After (n), the known superimposed uplink pilots P of the first communication device are subtracted from the uplink pilots P_Ul ¹(n)、P_Ul ²(n), an estimated value y of the downlink pilot frequency after passing through the downlink channel can be obtained_UP ¹(n)，y_UP ²And (n), recovering the downlink channel by using the known downlink pilot (the downlink pilot sent by the second communication device antenna 1 and the antenna 2 to the first communication device).

It should be noted that, the second communication device in this embodiment may be, but is not limited to, a base station, and the first communication device may be, but is not limited to, a terminal.

It will be understood by those skilled in the art that all or part of the steps in the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, where the program may be stored in a computer-readable storage medium, and when executed, the program may include the following steps: the second communication equipment receives the downlink pilot frequency sent by the first communication equipment, superposes the received downlink pilot frequency and the uplink pilot frequency to generate a mixed pilot frequency, and sends the mixed pilot frequency to the first communication equipment; the first communication equipment receives the mixed pilot frequency, estimates an uplink channel according to the received mixed pilot frequency and the known uplink pilot frequency, and acquires uplink channel parameters; the first communication equipment recovers and acquires the mixed pilot frequency transmitted by the second communication equipment according to the uplink channel parameters; and the first communication equipment acquires the downlink channel parameters according to the mixed pilot frequency, the known uplink pilot frequency and the known downlink pilot frequency transmitted by the second communication equipment. The storage medium referred to herein is, for example: ROM/RAM, magnetic disk, optical disk, etc.

As can be seen from the above, after each antenna of the first communication device applying the technical solution of this embodiment receives the downlink pilot sent by each antenna of the second communication device, all the downlink pilots received by the antenna are superimposed with the uplink pilot to be sent by the antenna to the second communication device, so as to generate a mixed pilot, and the mixed pilot is sent to the second communication device. After the second communication device receives the mixed pilot frequency, an uplink channel can be estimated according to the mixed pilot frequency and the predicted uplink pilot frequency; and according to the recovered mixed pilot frequency sent by the first communication device, the known downlink pilot frequency sent by the second communication device and the known uplink pilot frequency sent by the first communication device, the parameters of the downlink channel can be estimated. The method and the device can acquire the parameters of the downlink channel while estimating the uplink channel, and compared with the prior art, the technical scheme of the embodiment greatly reduces the signaling overhead for acquiring the parameters of the downlink channel.

In addition, since it is not necessary to obtain the downlink channel parameters by calculating the closed-loop channel parameters in this embodiment, for each uplink pilot and each downlink pilot, the delay spread length L of the uplink channel of the convolution result between them_ulIs zero (satisfies function (34)), without the delay spread length L in the closed-loop channel as required in embodiment 3_ul+L_dlIs zero (satisfies the functional formula (17)). The number of available pilot sequences due to the constraint of the function (17) is: N/(L)_ul+L_dl) Where N is the length of the OFDM symbol, and the number of available pilot sequences limited by the function (34) is: N/L_ul. It can be seen that: by applying the technical solution of this embodiment, compared with the technical solution of embodiment 3, the number of available pilots in an OFDM symbol can be greatly increased, and the pilot overhead is further reduced.

Example 5:

fig. 6 is a schematic structural diagram of a communication device provided in this embodiment, and as shown in the diagram, the communication device may include:

a receiving unit 601, configured to receive a downlink pilot sent by a second communication device, where the received downlink pilot may satisfy, in a time domain, a constraint condition represented by a function (11) in an embodiment.

A pilot coding unit 602, configured to superimpose the received downlink pilot and the uplink pilot to form a hybrid pilot.

The pilot encoding unit 602 may include:

uplink pilot coding section 6021 is configured to code the uplink pilot transmitted to the second communication device so that each uplink pilot satisfies the constraint conditions expressed by functional expressions (16) and (17) in embodiment 2.

Hybrid pilot coding section 6022 is configured to perform superposition coding on the uplink pilot obtained by coding in uplink pilot coding section 6021 and the downlink pilot received by receiving section 601.

Pilot encoding section 602 can ensure that the estimation of the uplink channel and the closed-loop channel is not affected by the superimposed downlink pilot after the second communication device receives the mixed pilot so that the generated mixed pilot satisfies the constraint conditions expressed by functional expressions (16) and (17) at the same time.

The coding superposition here is: and superposing the uplink pilot frequency and the downlink pilot frequency in a subcarrier of one OFDM symbol. In an OFDM system, the superimposed hybrid pilot behaves as: in one subcarrier of one OFDM symbol, a downlink pilot of a downlink channel between the second communication device and an uplink pilot of a corresponding uplink channel are included.

A sending unit 603, configured to send the hybrid pilot to a second communication device, which is typically a transmitting antenna.

It should be noted that, if the communication system supports the MIMO technology, the mixed pilots transmitted by each antenna are the mixed pilots that the pilot encoding unit 602 needs to transmit through the antenna, that is, the mixed pilots are: and superposing each downlink pilot frequency received by the antenna and transmitted by each antenna of the second communication equipment with an uplink pilot frequency which is required to be transmitted to the second communication equipment by the antenna.

The communication terminal may transmit the mixed pilot generated by the pilot encoding unit 602 to the second communication device through the transmission unit 603.

However, generally in combination with the processing in the related art, as shown in fig. 7, pilot coding section 602 may generate a mixed pilot, OFDM-modulate the generated mixed pilot with uplink data using modulation section 604, add a CP to the modulated OFDM signal using CP coding section 605, perform uplink transmission using transmitting section 603, and transmit the modulated OFDM signal to the second communication device.

The communication device of the present embodiment may be, but is not limited to being, a terminal.

As can be seen from the above, in the communication device provided in the embodiment of the present invention, the pilot encoding unit 602 performs mixing superposition on the downlink pilot received by the communication system and sent by the second communication device, and the uplink pilot to be sent by the communication system to the second communication device, and returns the received downlink pilot to the second communication device while transmitting the uplink pilot, so that the second communication device can estimate the uplink channel according to the received mixed pilot, the known uplink pilot, and the known downlink pilot, and estimate the downlink channel according to the estimated uplink channel, thereby obtaining the parameters of the downlink channel, where the specific processing procedure of the second communication device is detailed in the relevant descriptions in embodiments 3 and 4, and is not described herein. So that the second communication device can perform corresponding preprocessing (precoding, or pre-equalization) according to the downlink channel parameters.

Meanwhile, because the communication system enables the second communication device to acquire the parameters of the downlink channel by transmitting the mixed pilot frequency superposed by the downlink pilot frequency and the uplink pilot frequency, instead of performing corresponding downlink channel estimation at the communication device end as described in the prior art, and then transmitting the downlink channel parameters obtained by estimation along with the transmission of the uplink pilot frequency to the second communication device, so that the second communication device acquires the parameters of the downlink channel, the communication device applying the invention can avoid the complex processing of the communication system such as downlink channel estimation, precoding and the like, and also can avoid the distortion generated in the parameter transmission process of the downlink channel, in addition, because the pilot frequency coding unit 602 superposes the uplink pilot frequency and the uplink pilot frequency, the communication device applying the invention greatly reduces the pilot frequency overhead used for achieving the purpose of acquiring the downlink channel information by the second communication device compared with the prior art, the transmission resource cost is saved.

Example 6:

fig. 8 is a schematic structural diagram of another communication device provided in this embodiment, and as shown in the diagram, the communication device of this embodiment is different from the communication device shown in fig. 7 in embodiment 5 in that:

firstly, the method comprises the following steps: the receiving unit 801 in this embodiment replaces the receiving unit 601 in embodiment 5, where the receiving unit 801 is configured to receive a downlink pilot sent by the second communication device, where the received downlink pilot may meet the limitation condition represented by the functional expression (33) in the embodiment in a time domain.

Secondly, the method comprises the following steps: the second hybrid pilot coding unit 8022 and the uplink pilot coding unit 8021 in the pilot coding unit 802 in the present embodiment replace the hybrid pilot coding unit 6022 and the uplink pilot coding unit 6021 in the pilot coding unit 602 in embodiment 5, respectively.

The uplink pilot coding section 8021 in the present embodiment is configured to code the uplink pilot transmitted to the second communication apparatus so that each uplink pilot satisfies the constraint conditions expressed by the functional expressions (39) and (34) in embodiment 4.

The second hybrid pilot coding unit 8022 is configured to perform superposition coding on the uplink pilot determined by the uplink pilot coding unit 8021 and the downlink pilot received by the receiving unit 801.

Since the generated uplink pilot of the uplink pilot coding unit 8021 simultaneously satisfies the constraint conditions represented by the functional expressions (39) and (34), it can be ensured that the estimation of the uplink channel is not affected by the superimposed downlink pilot after the second communication device receives the mixed pilot.

As can be seen from the above, in the communication device provided in the embodiment of the present invention, the pilot encoding unit 802 performs mixing superposition on the downlink pilot sent by the second communication device and the uplink pilot to be sent by the communication system to the second communication device, and returns the received downlink pilot to the second communication device while transmitting the uplink pilot, so that the second communication device can estimate the uplink channel according to the received mixed pilot and the known uplink pilot, and can recover the channel of the received mixed pilot at the pilot transmitting end according to the estimated uplink channel, thereby obtaining the parameters of the downlink channel according to the recovered mixed pilot, the known downlink pilot and the known uplink pilot, and the specific processing procedure of the second communication device is described in embodiments 3 and 4, and will not be described in detail herein. So that corresponding preprocessing (precoding, or pre-equalization) can be performed according to the downlink channel parameters.

Meanwhile, similarly to embodiment 5, the communication device applying the present invention can avoid not only the complex processing of the communication system such as the estimation and precoding of the downlink channel, but also the distortion generated in the parameter transmission process of the downlink channel, and in addition, because the pilot coding unit 802 superimposes the uplink pilot and the uplink pilot, the communication device applying the present invention greatly reduces the pilot overhead used for achieving the purpose of acquiring the downlink channel information by the second communication device compared with the prior art, and saves the transmission resource cost.

Example 7:

fig. 9 is a schematic structural diagram of a communication device provided in this embodiment, and as shown in the diagram, the communication device may include:

a downlink pilot coding unit 901 is configured to code a downlink pilot sent to a second communication device, so that the downlink pilot satisfies the restriction conditions expressed by functional expressions (11) and (17) in embodiment 2. The uplink pilot signals in the functional expressions (11) and (17) satisfy the constraint condition represented by the functional expression (16) in the time domain. The above-mentioned limiting conditions can be such that: after the second communication device receives the downlink pilot, superimposes the downlink pilot and the uplink pilot to generate a mixed pilot, and sends the mixed pilot to the communication device of this embodiment, the communication device of this embodiment does not affect the estimation of the uplink channel or the closed-loop channel by the superimposed downlink pilot according to the mixed pilot.

The downlink pilot encoding unit 901 may directly superimpose the downlink pilot on the uplink pilot so that the downlink pilot satisfies the functional expressions shown in functional expressions (11) and (17) to avoid the second communication device to which the downlink pilot arrives from reprocessing the downlink pilot.

A sending unit 902, configured to send the downlink pilot generated by the downlink pilot encoding unit 901 to the second communication device.

A receiving unit 903, configured to receive a hybrid pilot sent by the second communication device, where the hybrid pilot is: and the second communication equipment receives superposition of the downlink pilot frequency and the uplink pilot frequency sent by the communication equipment.

Generally, the transmitting unit 902 and the receiving unit 903 may be antennas of the communication device.

An uplink channel estimating unit 904, configured to estimate an uplink channel according to the mixed pilot received by the receiving unit 903 and the known uplink pilot, and obtain an uplink channel parameter. The specific estimation process is described in detail in examples 1 and 2.

A closed-loop channel estimating unit 905, configured to estimate a closed-loop channel according to the mixed pilot received by the receiving unit 903 and the known downlink pilot, and acquire a closed-loop channel parameter. The specific estimation process is described in detail in examples 1 and 2.

A downlink channel estimating unit 906, configured to obtain a downlink channel parameter according to the closed-loop channel parameter obtained by estimation by the closed-loop channel estimating unit 905 and the uplink channel parameter obtained by estimation by the uplink channel estimating unit 904.

It should be noted that the communication device of this embodiment may be, but is not limited to, a base station, and correspondingly, the second communication device may be, but is not limited to, a terminal.

As can be seen from the above, the communication device provided in the embodiment of the present invention can estimate the uplink channel and the closed-loop channel according to the received mixed pilot, thereby estimating the downlink channel according to the estimated uplink channel and the estimated closed-loop channel, and acquiring the downlink channel parameters. So that corresponding preprocessing (precoding, or pre-equalization) can be performed according to the downlink channel parameters.

Example 8:

fig. 10 is a schematic structural diagram of the communication device provided in this embodiment, and as shown in the diagram, the communication device may include:

a downlink pilot coding section 1001 is configured to code a downlink pilot to be transmitted to a second communication device so that the downlink pilot satisfies constraint conditions expressed by functional expressions (33) and (34) in embodiment 4, where uplink pilots in the functional expressions (33) and (34) satisfy constraint conditions expressed by functional expression (39).

The above-mentioned limiting conditions can be such that: after the second communication device receives the downlink pilot, superimposes the downlink pilot and the uplink pilot to generate a mixed pilot, and sends the mixed pilot to the communication device of this embodiment, the communication device of this embodiment does not affect the uplink channel by the superimposed downlink pilot according to the mixed pilot, and can recover the signal of the mixed pilot at the second communication device according to the downlink pilot, thereby estimating and acquiring the parameter of the uplink channel.

A transmitting unit 1002, a receiving unit 1003, and an uplink channel estimating unit 1004, and they are the same as the transmitting unit 1002, the receiving unit 1003, and the uplink channel estimating unit 904 in embodiment 7, respectively.

A mixed pilot recovery unit 1005, configured to recover and acquire the mixed pilot sent by the second communication device, that is, recover and acquire the signal of the received mixed pilot at the transmitting end (second communication device) of the mixed pilot, according to the uplink channel parameter estimated and acquired by the uplink channel estimation unit 904 and the received mixed pilot. The specific working principle is described in detail in the relevant description of the embodiments 3 and 4.

A downlink channel estimating unit 1006, configured to estimate a downlink channel according to the hybrid pilot sent by the second communication device, the downlink pilot known to the communication device, and the uplink pilot estimated and obtained by the hybrid pilot recovering unit 1005, and obtain a downlink channel parameter. The specific working principle is described in detail in the relevant description of the embodiments 3 and 4.

As can be seen from the above, the communication device provided in the embodiment of the present invention can estimate an uplink channel according to the received mixed pilot, recover the signal of the received mixed pilot at the pilot transmitting end (second communication device) according to the estimated downlink channel, and obtain the downlink channel parameters according to the recovered mixed pilot by combining the known downlink pilot and uplink pilot. So that corresponding preprocessing (precoding, or pre-equalization) can be performed according to the downlink channel parameters.

It should be noted that the communication device of this embodiment may be implemented in the form of hardware, or may be implemented in the form of a software functional module. The device of the embodiment can be sold or used as a stand-alone product, and can also be stored in a computer readable storage medium.

The method and the communication device for acquiring channel information provided by the embodiment of the present invention are described in detail above, and a specific example is applied in the description to explain the principle and the implementation manner of the embodiment of the present invention, and the description of the embodiment is only used to help understanding the method and the principle of the embodiment of the present invention; meanwhile, general changes and substitutions within the technical scope of the present invention should be included in the protection scope of the present invention for those skilled in the art.

Claims (15)

1. A method for obtaining channel information, comprising:

the method comprises the steps that a first communication device receives a downlink pilot frequency sent by a second communication device, the received downlink pilot frequency and an uplink pilot frequency are overlapped to generate a mixed pilot frequency, and the mixed pilot frequency is sent to the second communication device;

the second communication equipment receives the mixed pilot frequency, estimates an uplink channel according to the received mixed pilot frequency and the known uplink pilot frequency, and acquires uplink channel parameters;

the second communication equipment estimates a closed-loop channel according to the known downlink pilot frequency and the received mixed pilot frequency to acquire closed-loop channel parameters;

and the second communication equipment acquires the downlink channel parameters according to the closed-loop channel parameters and the uplink channel parameters.

2. The method of claim 1, wherein the downlink pilot received by the first communication device comprises:

at least one antenna of the second communication device transmits downlink pilot frequency to the first communication device;

the uplink pilot frequency is as follows:

and the antenna of the first communication equipment transmits the uplink pilot frequency to the second communication equipment.

3. The method according to claim 1 or 2, wherein the downlink pilots sent by the antennas of the second communication device to the first communication device satisfy, in terms of time domain, the following form:

<math> <mrow> <munder> <mrow> <mi>&Sigma;</mi> </mrow> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> <mo>+</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein said p is_dl ^i*(t) is a downlink pilot p sent by the antenna i of the second communication device to the first communication device_dl ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by the antenna j of the second communication device to the first communication device_dlFor the delay spread length, L, of the downlink channel_ulThe time delay expansion length of an uplink channel is shown, a is a real number larger than zero, and i and j are both antenna identifiers of second communication equipment;

the uplink pilot frequency sent by each antenna of the first communication device to the second communication device satisfies the following form in the time domain:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein, the p is_ul ^i*(t) is the uplink pilot p sent by the antenna i of the first communication device to the second communication device_ul ⁱConjugation of (t), p_ul ^j(n-t) is an uplink pilot frequency sent by the antenna j of the first communication device to the second communication device, L_ulThe time delay expansion length of an uplink channel is shown, a is a real number larger than zero, and i and j are both antenna identifiers of the first communication equipment;

the uplink pilot frequencies and the downlink pilot frequencies meet the following conditions:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mrow> </math> 0＜n≤L_ul+L_dl，

wherein said p is_ul ^i*(t) is the uplink pilot p sent by the antenna i of the first communication device to the second communication device_ul ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by the antenna j of the second communication device to the first communication device_dlFor the delay spread length, L, of the downlink channel_ulFor the delay spread length of the uplink channel, a is a real number greater than zero, i and j are antennas of the first communication device and the second communication device respectivelyAnd (5) identifying.

4. The method of claim 3, wherein the first communication device transmitting the mixed pilot to the second communication device comprises:

the first communication equipment determines the ratio of the transmitting power allocated to each uplink pilot frequency to the constant transmitting power of the mixed pilot frequency, wherein the power for transmitting the mixed pilot frequency is not more than the preset mixed pilot frequency transmitting power upper limit;

the first communication equipment transmits the mixed pilot frequency to the second communication equipment according to the constant transmission power of the mixed pilot frequency and the ratios, and transmits the ratios to the second communication equipment;

the second communication device estimates an uplink channel according to the received mixed pilot and the known uplink pilot, and includes:

the second communication equipment determines the actual uplink pilot frequency according to the ratio values and the known uplink pilot frequency;

and the second communication equipment estimates each uplink channel according to the actual uplink pilot frequency and the received mixed pilot frequency.

5. The method of claim 3, wherein the first communication device transmitting the mixed pilot to the second communication device comprises:

the first communication equipment distributes the transmitting power distributed to each uplink pilot frequency to be constant power, wherein the transmitting power distributed to each uplink pilot frequency is smaller than the upper limit of the preset transmitting power of the mixed pilot frequency;

the first communication device determining a transmission power for transmitting the mixed pilot;

the first communication equipment transmits the mixed pilot frequency to the second communication equipment according to the transmitting power of each uplink pilot frequency and the transmitting power of the mixed pilot frequency;

the second communication device estimates an uplink channel according to the received mixed pilot and the known uplink pilot, and includes:

the second communication equipment determines the actual uplink pilot frequency according to the known transmitting power of each uplink pilot frequency;

and the second communication equipment estimates each uplink channel according to the actual uplink pilot frequency and the received mixed pilot frequency respectively.

6. A method for obtaining channel information, comprising:

the method comprises the steps that a first communication device receives a downlink pilot frequency sent by a second communication device, the received downlink pilot frequency and an uplink pilot frequency are overlapped to generate a mixed pilot frequency, and the mixed pilot frequency is sent to the second communication device;

the second communication equipment receives the mixed pilot frequency, estimates an uplink channel according to the received mixed pilot frequency and the known uplink pilot frequency, and acquires uplink channel parameters;

the second communication equipment recovers and acquires the mixed pilot frequency transmitted by the first communication equipment according to the uplink channel parameters;

and the second communication equipment acquires the downlink channel parameters according to the recovered and acquired mixed pilot frequency, known uplink pilot frequency and known downlink pilot frequency transmitted by the first communication equipment.

7. The method of claim 6, wherein the downlink pilot received by the first communication device comprises:

at least one antenna of the second communication device transmits downlink pilot frequency to the first communication device;

the uplink pilot frequency is as follows:

and the antenna of the first communication equipment transmits the uplink pilot frequency to the second communication equipment.

8. The method according to claim 6 or 7, wherein the downlink pilots sent by the antennas of the second communication device to the first communication device satisfy, in terms of time domain, the following form:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein said p is_dl ^i*(t) is a downlink pilot p sent by the antenna i of the second communication device to the first communication device_dl ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by the antenna j of the second communication device to the first communication device_dlThe time delay expansion length of a downlink channel is, a is a real number greater than zero, and i and j are both antenna identifiers of second communication equipment;

the uplink pilot frequency sent by each antenna of the first communication device to the second communication device satisfies the following form in the time domain:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein, the p is_ul ^i*(t) is the uplink pilot p sent by the antenna i of the first communication device to the second communication device_ul ⁱConjugation of (t), p_ul ^j(n-t) is an uplink pilot frequency sent by the antenna j of the first communication device to the second communication device, L_ulThe time delay expansion length of an uplink channel is shown, a is a real number larger than zero, and i and j are both antenna identifiers of the first communication equipment;

the uplink pilot frequencies and the downlink pilot frequencies meet the following conditions:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mrow> </math> 0＜n≤L_ul，

wherein said p is_ul ^i*(t) is the uplink pilot p sent by the antenna i of the first communication device to the second communication device_ul ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by the antenna j of the second communication device to the first communication device_ulAnd (3) the time delay expansion length of an uplink channel is shown, a is a real number greater than zero, and i and j are respectively antenna identifications of the first communication device and the second communication device.

9. The method of claim 8, wherein the first communication device transmitting the mixed pilot to the second communication device comprises:

the first communication equipment determines the ratio of the transmitting power allocated to each uplink pilot frequency to the constant transmitting power of the mixed pilot frequency, wherein the power for transmitting the mixed pilot frequency is not more than the preset mixed pilot frequency transmitting power upper limit;

the first communication equipment transmits the mixed pilot frequency to the second communication equipment according to the constant transmission power of the mixed pilot frequency and the ratios, and transmits the ratios to the second communication equipment;

the second communication device estimates an uplink channel according to the received mixed pilot and the known uplink pilot, and includes:

the second communication equipment determines the actual uplink pilot frequency according to the ratio values and the known uplink pilot frequency;

and the second communication equipment estimates each uplink channel according to the actual uplink pilot frequency and the received mixed pilot frequency.

10. The method of claim 8, wherein the first communication device transmitting the mixed pilot to the second communication device comprises:

the first communication equipment distributes the transmitting power distributed to each uplink pilot frequency to be constant power, wherein the transmitting power distributed to each uplink pilot frequency is smaller than the upper limit of the preset transmitting power of the mixed pilot frequency;

the first communication device determining a transmission power for transmitting the mixed pilot;

the first communication equipment transmits the mixed pilot frequency to the second communication equipment according to the transmitting power of each uplink pilot frequency and the transmitting power of the mixed pilot frequency;

the second communication device estimates an uplink channel according to the received mixed pilot and the known uplink pilot, and includes:

the second communication equipment determines the actual uplink pilot frequency according to the known transmitting power of each uplink pilot frequency;

and the second communication equipment estimates each uplink channel according to the actual uplink pilot frequency and the received mixed pilot frequency respectively.

11. A communication device, comprising:

a receiving unit, configured to receive a downlink pilot sent by a second communication device;

pilot frequency coding unit, which is used to superpose the received downlink pilot frequency and uplink pilot frequency to form mixed pilot frequency;

a sending unit, configured to send the hybrid pilot to the second communication device.

12. The communication device of claim 11, wherein the pilot coding unit comprises:

an uplink pilot coding unit, configured to code an uplink pilot transmitted to the second communication device, so that a form of each uplink pilot in a time domain satisfies:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein, the p is_ul ^i*(t) is the uplink pilot p sent by the antenna i of the communication device to the second communication device_ul ⁱConjugation of (t), p_ul ^j(n-t) is the uplink pilot frequency sent by the antenna j of the communication equipment to the second communication equipment, L_ulIs the time delay expansion length of the uplink channel, a is a real number larger than zero, i and j are both the antenna identifiers of the communication equipment,

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mrow> </math> 0＜n≤L_ul+L_dl，

wherein, the p is_ul ^i*(t) is the uplink pilot p sent by the antenna i of the communication device to the second communication device_ul ⁱConjugation of (t), p_dl ^j(n-t) is the downlink pilot frequency received by the receiving unit and issued by the antenna j of the second communication device to the communication device, and L_dlFor the delay spread length, L, of the downlink channel_ulThe time delay expansion length of an uplink channel is defined, a is a real number larger than zero, and i and j are respectively antenna identifiers of the communication equipment and the second communication equipment;

and the mixed pilot frequency coding unit is used for performing superposition coding on the uplink pilot frequency determined by the uplink pilot frequency coding unit and the downlink pilot frequency received by the receiving unit.

13. The communication device of claim 11, wherein the pilot coding unit comprises:

an uplink pilot coding unit, configured to code an uplink pilot transmitted to the second communication device, so that a form of each uplink pilot in a time domain satisfies:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein, the p is_ul ^i*(t) is the uplink pilot p sent by the antenna i of the communication device to the second communication device_ul ⁱConjugation of (t), p_ul ^j(n-t) is the uplink pilot frequency sent by the antenna j of the communication equipment to the second communication equipment, L_ulIs the delay spread length of the uplink channel, a is a real number greater than zero,

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mrow> </math> 0＜n≤L_ul，

wherein said p is_ul ^i*(t) is the uplink pilot p sent by the antenna i of the communication device to the second communication device_ul ⁱConjugation of (t), p_dl ^j(n-t) of the second communication device received by the receiving unitDownlink pilot frequency L transmitted by antenna j to the communication equipment_ulA is a real number greater than zero and is the delay spread length of an uplink channel;

and the mixed pilot frequency coding unit is used for performing superposition coding on the uplink pilot frequency determined by the uplink pilot frequency coding unit and the downlink pilot frequency received by the receiving unit.

14. A communication device, comprising:

a downlink pilot frequency coding unit, configured to code a downlink pilot frequency issued to a second communication device, so that a form of the downlink pilot frequency in a time domain satisfies:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> <mo>+</mo> <msub> <mi>L</mi> <mi>ul</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein said p is_dl ^i*(t) is downlink pilot p sent by antenna i of the communication device to the second communication device_dl ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by an antenna j of the communication equipment to the second communication equipment_dlFor the delay spread length, L, of the downlink channel_ulIs the delay spread length of the uplink channel, a is a real number greater than zero,

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mrow> </math> 0＜n≤L_ul+L_dl，

wherein, the p is_ul ^i*(t) uplink pilot p for transmission from antenna i of second communication device to this communication device_ul ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by an antenna j of the communication equipment to the second communication equipment_dlFor the delay spread length, L, of the downlink channel_ulA is a real number greater than zero and is the delay spread length of an uplink channel;

a sending unit, configured to send the downlink pilot generated by the downlink pilot encoding unit to the second communication device;

a receiving unit, configured to receive the hybrid pilot sent by the second communication device, where the hybrid pilot is: the second communication equipment receives superposition of the downlink pilot frequency and the uplink pilot frequency sent by the communication equipment;

an uplink channel estimation unit, configured to estimate an uplink channel according to the hybrid pilot and a known uplink pilot, and obtain an uplink channel parameter;

a closed-loop channel estimation unit, configured to estimate a closed-loop channel according to the received mixed pilot and a known downlink pilot, and obtain closed-loop channel parameters;

and the downlink channel estimation unit is used for acquiring the downlink channel parameters according to the closed-loop channel parameters and the uplink channel parameters.

15. A communication device, comprising:

a downlink pilot frequency coding unit, configured to code a downlink pilot frequency issued to a second communication device, so that a form of the downlink pilot frequency in a time domain satisfies:

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfenced open='{' close=''> <mtable> <mtr> <mtd> <mi>a</mi> </mtd> <mtd> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> <mo>&lt;</mo> <mi>n</mi> <mo>&le;</mo> <msub> <mi>L</mi> <mi>dl</mi> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

wherein said p is_dl ^i*(t) communication from the antenna i of the second communication device to the home communication deviceDownlink pilot frequency p issued by equipment_dl ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency, L, issued by the antenna j of the second communication device to the communication device_dlIs the delay spread length of the downlink channel, a is a real number greater than zero,

<math> <mrow> <munder> <mi>&Sigma;</mi> <mi>n</mi> </munder> <msup> <msubsup> <mi>p</mi> <mi>ul</mi> <mi>i</mi> </msubsup> <mo>*</mo> </msup> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <msubsup> <mi>p</mi> <mi>dl</mi> <mi>j</mi> </msubsup> <mrow> <mo>(</mo> <mi>n</mi> <mo>-</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> </mrow> </math> 0＜n≤L_ul，

wherein, the p is_ul ^i*(t) uplink pilot p for transmission from antenna i of second communication device to this communication device_ul ⁱConjugation of (t), p_dl ^j(n-t) is a downlink pilot frequency (L) sent by an antenna j of the communication equipment to the second communication equipment_dlFor the delay spread length, L, of the downlink channel_ulA is a real number greater than zero and is the delay spread length of an uplink channel;

a sending unit, configured to send the downlink pilot generated by the downlink pilot encoding unit to the second communication device;

a receiving unit, configured to receive the hybrid pilot sent by the second communication device, where the hybrid pilot is: the second communication equipment receives superposition of the downlink pilot frequency and the uplink pilot frequency sent by the communication equipment;

an uplink channel estimation unit, configured to estimate an uplink channel according to the hybrid pilot and a known uplink pilot, and obtain an uplink channel parameter;

a mixed pilot recovery unit, configured to recover and acquire the mixed pilot sent by the second communication device according to the uplink channel parameter and the received mixed pilot;

and a downlink channel estimation unit, configured to obtain a downlink channel parameter according to the hybrid pilot, the known downlink pilot, and the known uplink pilot sent by the second communication device.

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