CN101282198A - Uplink multi-antenna transmission method and terminal in Time Division Duplex (TDD) system - Google Patents

Abstract

The invention discloses a transmission method of uplink multi-antenna in Time Division Duplex (TDD) system, the terminal in the TDD system has at least two transmitting antennas, the method is: the terminal carries out channel estimation according to the public reference symbol sent by the base station to obtain the state information of a downlink channel; determining a time delay value used by each transmitting antenna when transmitting uplink circulating time delay diversity according to the state information of the downlink channel; and according to the time delay value, performing uplink transmission on each transmitting antenna of the mobile terminal. The invention also discloses a transmission terminal of the uplink multi-antenna in the TDD system. The invention can determine the delay value according to the channel characteristic when the terminal carries out the uplink circulation delay diversity transmission in the TDD system, so that the terminal has better performance.

Description

An uplink multi-antenna transmission method and terminal in a time division duplex TDD system

technical field

The present invention relates to the technical field of wireless communication, in particular to an uplink multi-antenna transmission method and a terminal in a time division duplex TDD system.

Background technique

Orthogonal Frequency Division Multiplexing (OFDM) is a broadband transmission technology suitable for application in multipath environments, but the OFDM system itself does not have diversity capabilities, so it is necessary to use corresponding diversity techniques to obtain higher reliability . In the OFDM system of DVB-T and HIPERLAN/2, the frequency domain is interleaved, and in the frequency selective channel, the performance of the convolutional decoder can be improved. But for flat fading channels, performance gains cannot be obtained in this way. The space-time coding technology based on the diversity maximization strategy can obtain diversity and coding gain through redundant information and coding relationships introduced in space and time, but conventional space-time coding schemes require the receiver to perform corresponding space-time decoding. This increases the complexity of the receiver.

Delay Diversity (DD) is a space diversity technique of OFDM system. The sender in the DD system uses multiple antennas for transmission, and the signals sent on different antenna elements have different delays. The artificial delay extension makes the equivalent channel produce frequency selectivity, and the forward error control (FEC ) mechanism can use this frequency selectivity to generate frequency diversity gain and improve the error probability performance of the system. The receiver structure of the DD system is exactly the same as that of the single-antenna receiver, and no additional processing modules are required. However, in order to avoid the Inter Symbol Interference (ISI) caused by DD, the delay must be limited by the size of the Guard Period (GP) slot in the wireless frame.

In order to avoid the above problems, in a cyclic delay diversity (Cyclic Delay Diversity, CDD) system, the signals of each antenna branch are sent in parallel after cyclic offset. Since there is no real delay between the signals of each antenna branch, there will be no ISI problem, and the cyclic offset will not be limited by the GP. For the receiving end, the cyclic offset is only equivalent to the change of the equivalent channel, so it does not increase the complexity of the receiver. CDD can also be considered as a kind of space-time coding. Compared with some other space-time coding technologies, CDD has no limitation on the number of antennas and no rate loss.

Assuming that the number of samples in an OFDM symbol is N _F , the number of transmitting antennas in the CDD system is N, and the cyclic delay on the nth antenna branch relative to the first antenna is $0\≤{\mathrm{\δ}}_{\mathrm{no}}^{\mathrm{Cy}}\≤\frac{N_f}{2},$ where n=0, . . . , N-1. In general, the delay between any two adjacent antennas is the same, called delay increment, assumed to be τ, and, $0\≤\mathrm{\τ}\≤\frac{N_f}{2(N-1)},$ N>1, then

${\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; CF</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}$

${\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; CF</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}$

...

${\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; CF</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}$

...

${\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}^{\mathrm{<span\; class="notranslate">\; CF</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}$

The principle of the OFDM system transmitter using CDD can be shown in Figure 1:

After the input signal undergoes FEC, interleaving, modulation and inverse fast Fourier transform (IFFT), it is distributed to N antenna branches, and the signals on each antenna branch have different cyclic delays. Without loss of generality, the cyclic delay of the first antenna branch is set to 0. Since the cyclic delays of multiple branches are superimposed after channel transmission, it is equivalent to multipath propagation for the receiver. However, after CDD is adopted, the receiver does not need additional processing procedures such as merging (except channel estimation), and does not increase the complexity of the receiver. After removing the cyclic prefix (CP), the receiver directly performs Fast Fourier Transform (FFT), M-channel Maximum Ratio Combining (MRC), demodulation, deinterleaving, and decoding. The receiver structure is shown in Figure 2.

The CDD signal on antenna n can be represented by Inverse Discrete Fourier Transform (IDFT) as

Among them, l represents the discrete time and k represents the discrete frequency. Define the phase shift sequence

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}\mathrm{<span\; class="notranslate">\; k</span>}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; Cy</span>}}}<span\; class="notranslate">\; ,</span>$

It can be seen from the above description that the CDD signal on the antenna n is equivalent to performing OFDM modulation on the frequency domain signal S(k) after phase deflection by C _n (k), so that the phase diversity (Phase diversity) of the CDD signal can be obtained. Diversity, PD) equivalent implementation is shown in Figure 3.

The cyclic delay of CDD appears before the cyclic prefix, and the equivalent delay offset is not limited by CP but only limited by OFDM modulation, so the equivalent channel can be improved without increasing the actual signal delay extension. frequency selectivity. If h _{m, n} (k) is the channel transfer function from the nth transmitting branch to the mth receiving branch on the kth subcarrier, then the equivalent channel transfer function corresponding to the mth receiving antenna can be expressed as:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; eq</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>$

It can be seen from the above formula that the frequency selectivity of the equivalent channel transfer function is improved.

It can be seen from the above formula that to synthesize the equivalent channel transfer function, the receiver needs to estimate the channel transfer function h _m,n (k) from each transmit antenna to the receive antenna, and obtain the phase offset sequence C _n (k). In order for the receiver to estimate the channel transfer function h _m,n (k) from each transmit antenna to the receive antenna, the transmit antennas of the transmitter need to transmit mutually orthogonal pilot symbols, and the receiver uses the pilot symbols to perform h _m,n ( The estimation of k) refers to the pilot used for channel estimation, demodulation and detection as demodulation (Demodulation, DM) pilot. Since cyclic delay and other transmit diversity or other preprocessing is generally not performed on the common pilot, the receiver must know the delay of each transmit antenna of the transmitter in advance, and the receiver obtains the phase offset sequence C _n (k) according to the delay , and then the equivalent channel transfer function can be synthesized. The amount of cyclic delay of each transmitting antenna branch is generally selected as a fixed amount in each cell, and this parameter needs to be notified to the receiver through signaling.

At the same time, in the existing system, both uplink and downlink need to measure channel quality through specific pilot symbols, and this kind of pilot is called channel quality indicator (Channel Quality Indicator, CQI) pilot. Similar to the DM pilot, the transmitter does not perform cyclic delay diversity on the CQI pilot, and the transmitter needs to transmit mutually orthogonal CQI pilots on different transmit antennas. The uplink CQI measurement is processed by the base station. After measuring the CQI in the downlink, the terminal needs to give feedback to the base station. The base station performs resource scheduling and modulation and coding scheme (Modulation & Coding Scheme, MCS) selection according to the tracking of the CQI of the link.

Visible, there is following shortcoming in prior art:

(1) The terminal cannot select the amount of delay according to the channel characteristics;

In the existing time division duplex (TDD) system, when the terminal performs cyclic delay diversity processing on the uplink data, the delay amount used is a preset fixed delay amount, which cannot match the channel characteristics, causing system errors low probabilistic performance;

(2) The terminal needs to notify the receiver in advance of the used delay amount through signaling;

When the base station performs CDD equivalent channel estimation, that is, when performing the synthesis of the equivalent channel transfer function, it is synthesized by estimating the channel response of each transmitting antenna branch and the delay amount known in advance, then the terminal must pass the signaling Inform the base station of the CDD delay used. If the terminal adjusts the CDD time delay, it must send corresponding signaling again to inform the receiver of the adjusted CDD time delay, which increases the signaling overhead between the terminal and the base station.

(3) The terminal needs to send mutually orthogonal CQI pilots on different transmit antennas;

The terminal needs to send orthogonal CQI pilots on different transmit antennas, and the base station performs channel quality measurement based on the CQI pilots. The design complexity of the CQI pilots and related pilot measurement work are relatively complicated.

Contents of the invention

The present invention provides an uplink multi-antenna transmission method and terminal in a time division duplex TDD system, which is used to solve the problem that the terminal in the TDD system in the prior art cannot determine the time delay according to the channel characteristics when performing uplink cyclic delay diversity transmission amount, which leads to the problem of low system error probability performance.

The transmission method of uplink multi-antenna in a kind of time division duplex TDD system provided by the present invention comprises the following steps:

A. The terminal performs channel estimation according to the common reference symbol sent by the base station, and obtains the state information of the downlink channel;

B. The terminal determines, according to the state information of the downlink channel, the delay value used by each transmit antenna of itself during uplink cyclic delay diversity transmission;

C. The terminal performs uplink transmission on each of its transmit antennas according to the delay value.

The state information of the downlink channel includes a downlink channel transmission matrix, and step B includes:

B0. The terminal obtains an uplink channel transmission matrix by using the downlink channel transmission matrix, and the uplink channel transmission matrix is a transposition matrix of the downlink channel transmission matrix;

B1. The terminal uses the uplink channel transmission matrix to determine the delay value used by each of its transmit antennas during uplink cyclic delay diversity transmission.

When the terminal saves more than one delay value increment, and the uplink resource blocks used by the terminal use the same delay value during uplink cyclic delay diversity transmission, then step B1 includes:

For each delay value increment, determine the effective signal-to-noise ratio corresponding to the delay value increment, and the determination method is: for the subcarriers in each uplink resource block, use the maximum effective signal-to-noise ratio mapping The method, according to the delay value increment and the uplink channel transmission matrix, obtains the effective signal-to-noise ratio corresponding to the delay value increment;

Select the delay value increment corresponding to the largest effective signal-to-noise ratio among the obtained effective signal-to-noise ratios, and determine the time delay used when each transmit antenna of the terminal performs cyclic delay diversity transmission according to the delay value increment value.

When the terminal saves more than one delay value increment, and the uplink resource blocks used by the terminal use different delay values during uplink cyclic delay diversity transmission, then step B1 includes:

For each uplink resource block, determine the delay value used when each transmit antenna of the terminal uses the uplink resource block to perform cyclic delay diversity transmission, and the determination method is as follows:

For each delay value increment, for the subcarriers in the uplink resource block, use the maximum effective signal-to-noise ratio mapping method to obtain the delay value according to the delay value increment and the uplink channel transmission matrix The effective signal-to-noise ratio corresponding to the value increment; select the time delay value increment corresponding to the maximum effective signal-to-noise ratio in the obtained effective signal-to-noise ratio, and determine the use of each transmitting antenna of the terminal according to the time delay value increment The delay value used when the uplink resource block performs cyclic delay diversity transmission.

Step C includes:

The terminal uses the delay value to send the uplink data and the demodulated DM pilot for demodulating the data to the base station after cyclic delay diversity processing.

The method further includes:

The terminal uses the delay value to send the CQI pilot used for uplink channel quality indicator CQI estimation to the base station after cyclic delay diversity processing.

The method further includes:

The terminal sends mutually orthogonal CQI pilots to the base station on each of its transmit antennas, and feeds back the time delay value to the base station.

The present invention also provides a terminal for uplink multi-antenna transmission in a time division duplex TDD system, the terminal is used for:

Perform channel estimation according to the common reference symbol sent by the base station, and obtain the state information of the downlink channel; determine the time delay value used by each transmit antenna for uplink cyclic delay diversity transmission according to the state information of the downlink channel; According to the delay value, uplink transmission is performed on each transmit antenna.

The terminal includes:

The receiving unit is used to receive the common reference symbol sent by the base station, perform channel estimation according to the common reference symbol, and obtain the state information of the downlink channel;

A determining unit, configured to determine a delay value used by each transmit antenna of the terminal during uplink cyclic delay diversity transmission according to the state information of the downlink channel;

The transmission unit is configured to perform uplink transmission on each transmit antenna of the terminal according to the delay value.

The determination unit includes:

An uplink unit, configured to use the downlink channel transmission matrix in the downlink channel state information to obtain an uplink channel transmission matrix, where the uplink channel transmission matrix is a transposition matrix of the downlink channel transmission matrix;

The delay value unit is configured to use the uplink channel transmission matrix to determine the delay value used by each transmit antenna of the terminal during uplink cyclic delay diversity transmission.

The delay value unit includes:

a storage unit for storing more than one delay value increment;

The first calculation unit is configured to determine the delay value increment for each delay value increment when the uplink resource blocks used by the terminal use the same delay value during uplink cyclic delay diversity transmission. The effective signal-to-noise ratio corresponding to the quantity, the determination method is: for the subcarriers in each uplink resource block, using the maximum effective signal-to-noise ratio mapping method, according to the delay value increment and the uplink channel transmission matrix , to obtain the effective signal-to-noise ratio corresponding to the delay value increment; select the delay value increment corresponding to the largest effective signal-to-noise ratio among the obtained effective signal-to-noise ratios, and determine each time delay value of the terminal according to the delay value increment The delay value used when the transmit antennas perform cyclic delay diversity transmission.

The second calculation unit is configured to determine each transmission of the terminal for each uplink resource block when the uplink resource blocks used by the terminal use different delay values during uplink cyclic delay diversity transmission The delay value used when the antenna uses the uplink resource block to perform cyclic delay diversity transmission is determined by using the maximum effective The signal-to-noise ratio mapping method, according to the delay value increment and the uplink channel transmission matrix, obtains the effective signal-to-noise ratio corresponding to the delay value increment; A delay value increment, determining a delay value used when each transmit antenna of the terminal uses the uplink resource block to perform cyclic delay diversity transmission according to the delay value increment.

The transfer unit is used for:

Using the delay value, the uplink data and the demodulated DM pilot for demodulating the data are processed by cyclic delay diversity and then sent to the base station.

The transfer unit is also used for:

Using the delay value, the CQI pilot used for uplink channel quality indicator CQI estimation is processed by cyclic delay diversity and sent to the base station.

The transfer unit is also used for:

Send mutually orthogonal CQI pilots to the base station on each transmit antenna of the terminal, and feed back the time delay value to the base station.

With the present invention, in the TDD system, the terminal uses the reciprocity of the uplink and downlink channels of the TDD system, uses the channel information measured in the downlink channel to obtain the channel information of the uplink channel, and then determines the time delay of uplink CDD transmission according to the channel information of the uplink channel The value realizes the adaptive selection of the delay value of CDD transmission according to the channel characteristics, and improves the error probability performance of the system.

At the same time, the terminal uses the determined delay value to perform CDD processing on the DM pilot or CQI pilot before performing uplink transmission. Different transmit antennas of the terminal can use the same DM pilot or the same CQI pilot, thus saving pilots. Design complexity.

In addition, the terminal uses the determined delay value to perform CDD processing on the DM pilot and the CQI pilot before uplink transmission. For the reception of the base station in the uplink, it is not necessary to know the distance from each terminal transmit antenna to the base station receive antenna. The channel response between the arrays can directly estimate the equivalent CDD channel, and then perform data detection and CQI measurement. Therefore, the signaling overhead of sending each antenna delay value to the base station receiver can be saved.

Description of drawings

FIG. 1 is a schematic diagram of the working principle of a transmitter of an OFDM system using CDD in the prior art;

FIG. 2 is a schematic diagram of the working principle of a receiver of an OFDM system using CDD in the prior art;

FIG. 3 is a schematic diagram of an equivalent implementation manner of phase diversity of CDD in the prior art;

Fig. 4 is the schematic flow chart of the method provided by the present invention;

FIG. 5 is a schematic flow diagram of a method embodiment provided by the present invention;

FIG. 6 is a schematic diagram of a terminal structure provided by the present invention.

Detailed ways

The present invention provides an uplink multi-antenna transmission method in a TDD system. In a TDD system, when a terminal has multiple transmit antennas, a cyclic delay diversity technique can be used for uplink transmission, see FIG. 4 , specifically including:

Step 401: the terminal obtains the state information of the downlink channel according to the received downlink common reference symbol from the base station;

Step 402: The terminal determines the delay value during uplink CDD transmission according to the obtained state information of the downlink channel;

Step 403: The terminal sends uplink transmission according to the determined delay value;

This step specifically includes:

The uplink data and the DM pilot used to demodulate the data are uniformly processed by CDD, that is, the data transmitted on the same transmitting antenna and the DM pilot are transmitted with the same delay value, and different transmitting antennas can use the same DM pilot;

The CQI pilots used for uplink CQI estimation are processed by CDD, and only one set of CQI pilots for estimating CQI is needed at this time; or, the CQI pilots used for uplink CQI estimation are not processed by CDD, and at this time they need to be transmitted in different Different groups of CQI pilots are transmitted on the antenna, and the groups of CQI pilots are orthogonal to each other.

Below in conjunction with specific embodiment, the present invention is described:

In this embodiment, it is assumed that the number of base station antennas is M, and the number of terminal antennas is N. During downlink transmission, the base station uses M antennas for transmission, and the terminal uses N antennas for reception. The downlink channel transmission matrix is H ^DL ∈ C ^N×M . Referring to Figure 5, the terminal adaptively selects the amount of delay and uplink CDD transmission specifically includes:

Step 501: the base station sends mutually orthogonal common reference symbols to the terminal on multiple antennas;

Step 502: the terminal obtains downlink channel state information by using the received common reference symbol from the base station;

Here, the terminal estimates the mth column of ^HDL by using the common reference symbols transmitted by the mth transmit antenna of the base station, and by using the pilot symbols transmitted by the M base station antennas, the terminal can obtain the complete downlink channel transmission matrix H ^DL .

Step 503: The terminal obtains the state information of the uplink channel according to the state information of the downlink channel by using the reciprocity of the uplink and downlink channels of the TDD system;

Here, the terminal can directly obtain the uplink channel transmission matrix H ^UL =(H ^DL ) ^T from the downlink channel transmission matrix H ^DL by using the reciprocity of the uplink and downlink channels in the TDD system.

Step 504: The terminal determines the delay value during uplink CDD transmission according to the status information of the uplink channel;

Here, the terminal directly uses the uplink channel transmission matrix to determine the delay value during uplink CDD transmission, that is, δ _n ^CY . When determining δ _n ^CY , the CDD transmission delay value can be determined by using the criterion of maximizing the effective signal-to-noise ratio:

The equivalent channel on the mth antenna on the kth subcarrier at the receiving end is:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; eq</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; UL</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>$

in $C_{\mathrm{no}}\left(k\right)=e^{-j\frac{2\mathrm{\&pi;}}{N_f}k{\mathrm{\&delta;}}_{\mathrm{no}}^{\mathrm{Cy}}},$ h _m,n ^UL (k) is the transfer function from the nth transmitting antenna to the mth receiving antenna in the uplink channel transmission matrix H ^UL (k).

Then, the output signal-to-noise ratio on each subcarrier k at the receiver is:

${\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; m</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; eq</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Among them, σ ² is the receiving noise, assuming that the noise of each receiving antenna is the same.

Assuming that the effective signal-to-noise ratio is calculated using the maximized effective signal-to-noise ratio mapping (EESM) method, then the effective signal-to-noise ratio is:

${\mathrm{<span\; class="notranslate">\; SNR</span>}}_{\mathrm{<span\; class="notranslate">\; eff</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

Among them, β is a parameter related to modulation and coding used in an EESM mapping method, which can be determined in advance through simulation. k is the sequence number of subcarriers used by the user to transmit data, and K is the total number of these subcarriers.

Assuming that the system has given a set of optional delay value increments τ _l in advance, l=0...L-1, where L is the system specified

Assume that the system has given a group of optional delay value increments τ _l in advance, l=0...L-1, where L is the size of the delay value group specified by the system. As shown in the following table, it is a set of optional delay values in the case of L=8:

Then, the effective signal-to-noise ratio corresponding to different delay value increments τ _l can be written as:

${\mathrm{<span\; class="notranslate">\; SNR</span>}}_{\mathrm{<span\; class="notranslate">\; eff</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

$<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; K</span>}}\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\frac{\underset{\mathrm{<span\; class="notranslate">\; m</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}\mathrm{<span\; class="notranslate">\; k\; n</span>}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; UL</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

................................................... .[1]

According to the formula [1], the terminal can determine the transmission delay of each antenna by selecting the delay increment value τ′ corresponding to the maximum effective SNR ${\mathrm{\&delta;}}_{\mathrm{no}}^{\mathrm{Cy}}=\mathrm{no}{\mathrm{\&tau;}}^{\&prime;}.$

Specifically, in the uplink resource blocks used by a terminal, different resource blocks may use the same CDD delay amount, or different resource blocks may use different delay amounts.

If all resource blocks use the same delay value, K includes the subcarriers in all resource blocks when calculating the effective SNR. At this time, only one set of effective SNR needs to be calculated, that is, for each delay value increasing The delay increment value τ' is used to determine the transmission delay value of each antenna.

If the delay value used by each resource block is different, it is necessary to calculate a set of effective signal-to-noise ratios for each resource block, and then select the delay value increment τ′ corresponding to the maximum effective signal-to-noise ratio in the set of effective signal-to-noise ratios , according to the delay value increment τ′, determine the delay amount used when the corresponding resource block performs uplink transmission. The specific method for calculating the effective SNR for a resource block is: for each delay value increment τ _l , calculate its corresponding effective SNR according to the formula [1], and use the resource block included in the specific calculation Subcarrier k is calculated, that is, k at this time means the sequence number of a subcarrier in a resource block, and K is the number of subcarriers in a resource block.

Step 505: The terminal sends uplink data, DM pilot and CQI pilot according to the determined CDD transmission delay value;

After determining the CDD transmission delay value of each transmit antenna, the terminal performs CDD transmission on the uplink data according to the delay value.

Since the uplink DM pilot is not used by other users, the DM pilot and uplink data can be transmitted after CDD processing, that is, the data transmitted on the same transmit antenna and the DM pilot are transmitted with the same delay value. The selection of the time delay on each antenna branch does not need to be notified to the base station through signaling. The base station directly uses the received DM pilot which has been processed by CDD to estimate the equivalent channel and receive data.

In addition, in the present invention, the CQI pilot can also be sent to the base station after CDD processing, and the following method can be used to determine its specific delay value:

If all resource blocks used for uplink user data transmission use the same delay value, then the resource blocks covered by the CQI reference symbols fed back by each user also use the same delay value, and K includes the user when calculating the delay value The subcarriers in all resource blocks covered by the CQI reference symbols are fed back, and the delay value of data transmission is determined by the delay value of the CQI reference symbols. If the delay value used for each resource block used for uplink user data transmission is different, then the resource blocks covered by the CQI reference symbol fed back by each user also use a different delay value. When calculating the delay value, as long as Each resource block can be calculated using its corresponding subcarrier.

Using the above method, it can be ensured that the cyclic delay value applied to the CQI pilot is the same as the uplink data and the delay value used by the DM pilot for demodulating the data, so that the CQI value calculated by the base station is valid.

When the CQI pilot used for CQI estimation does not perform cyclic delay diversity processing, the terminal needs to inform the base station of the cyclic delay value through the feedback channel, and the base station can perform Estimation of CQI. Specifically, if the delay value used by each resource block of the terminal is different, the terminal needs to inform the base station of the delay value corresponding to each resource block occupied by the CQI pilot; if all physical resource blocks of the terminal use the same delay value, then the terminal only needs to feed back a delay value. For example, the sequence number 1 of the determined delay value increment _τl may be fed back to the base station.

After receiving the CDD-processed signal, the base station uses the received CDD-processed pilot signal and the terminal's original pilot data before CDD processing to perform channel estimation, and then perform data demodulation or channel quality estimation. The specific method as follows:

Denote the original pilot as P, and the signal form of the pilot after the terminal CDD processing reaches the mth antenna of the receiving end can be expressed as

Among them, r(k) represents the received signal on the kth subcarrier, and n(k) represents the noise and interference on the kth subcarrier. According to r(k) and the known original pilot P(k), the equivalent channel h _m ^(eq) (k) can be estimated by conventional channel estimation methods, and the data demodulation can be performed by using the channel estimation results Or channel quality estimation.

Visible, the present invention can produce following beneficial effect with respect to prior art:

The terminal can adaptively select the time delay of each antenna according to the channel characteristics, which improves the error probability performance of the system. This method makes full use of the reciprocity of the uplink and downlink channels of the TDD system, and uses the channel information measured in the downlink channel to adjust the parameters of uplink CDD transmission, so that it has better performance.

At the same time, different transmit antennas of the terminal can use the same DM pilot and CQI pilot, thus saving the complexity of pilot design. Since the selection of CDD delay parameters is determined by the terminal, for the reception of the base station in the uplink, it is not necessary to know the channel response between each terminal transmit antenna and the base station receive antenna array, but the equivalent CDD The channel is estimated to perform data detection and CQI measurement.

In addition, the signaling overhead of sending the time delay of each antenna to the base station receiver can also be saved. The terminal independently determines the CDD delay, but the base station may not know the CDD delay when performing data detection and CQI estimation, so the signaling overhead for coordinating the CDD delay between the base station and the terminal can be omitted.

Referring to Fig. 6, the present invention also provides a terminal for uplink multi-antenna transmission in a time division duplex TDD system, the terminal is used for: performing channel estimation according to the common reference symbol sent by the base station, and obtaining state information of the downlink channel; The state information of the downlink channel is used to determine the delay value used by each transmit antenna in uplink cyclic delay diversity transmission; according to the delay value, perform uplink transmission on each transmit antenna.

The terminal includes a receiving unit 601, a determining unit 602, and a transmitting unit 603, wherein the receiving unit 601 is used to receive the common reference symbol sent by the base station, perform channel estimation according to the common reference symbol, and obtain the state information of the downlink channel; the determining unit 602, configured to determine, according to the state information of the downlink channel, the delay value used by each transmit antenna of the terminal during uplink cyclic delay diversity transmission; the transmission unit 603 is configured to, according to the delay value, transmit the delay value at each transmit antenna of the terminal Uplink transmission is carried out on a transmit antenna.

The determination unit 602 includes an uplink unit 6021 and a delay value unit 6022, wherein the uplink unit 6021 is configured to use the downlink channel transmission matrix in the downlink channel state information to obtain an uplink channel transmission matrix, the uplink channel transmission matrix is the The transposition matrix of the downlink channel transmission matrix; the delay value unit 6022, configured to use the uplink channel transmission matrix to determine the delay value used by each transmit antenna of the terminal during uplink cyclic delay diversity transmission.

The delay value unit 6022 includes a storage unit 60221, a first calculation unit 60222 and a second calculation unit 60223, wherein the storage unit 60221 is used to store more than one delay value increment; When the uplink resource blocks used by the terminal use the same delay value during uplink cyclic delay diversity transmission, for each delay value increment, determine the effective signal-to-noise ratio corresponding to the delay value increment, and determine The method is: for the subcarriers in each uplink resource block, using the mapping method of maximizing the effective signal-to-noise ratio, according to the delay value increment and the uplink channel transmission matrix, to obtain the delay value increment corresponding to The effective signal-to-noise ratio; select the delay value increment corresponding to the largest effective signal-to-noise ratio in the obtained effective signal-to-noise ratio, and determine each transmit antenna of the terminal according to the delay value increment to perform cyclic delay diversity transmission The delay value used when . The second calculation unit 60223 is configured to determine, for each uplink resource block of the terminal, when the uplink resource blocks used by the terminal use different delay values during uplink cyclic delay diversity transmission The delay value used when the transmitting antenna uses the uplink resource block to perform cyclic delay diversity transmission is determined by: for each delay value increment, for the subcarriers in the uplink resource block, use the maximum The effective signal-to-noise ratio mapping method, according to the delay value increment and the uplink channel transmission matrix, obtains the effective signal-to-noise ratio corresponding to the delay value increment; selects the largest effective signal-to-noise ratio corresponding to the obtained effective signal-to-noise ratio The delay value increment is determined according to the delay value increment, and the delay value used when each transmit antenna of the terminal uses the uplink resource block to perform cyclic delay diversity transmission is determined.

The transmission unit 603 is configured to: use the delay value to send the uplink data and the DM pilot for demodulating the data to the base station after cyclic delay diversity processing.

The transmission unit 603 is further configured to: use the delay value to send the CQI pilot used for uplink channel quality indicator CQI estimation to the base station after cyclic delay diversity processing. Alternatively, mutually orthogonal CQI pilots are sent to the base station on each transmit antenna of the terminal, and the time delay value is fed back to the base station.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (14)

1. A transmission method of uplink multi-antenna in a time division duplex TDD system, the terminal in the TDD system has at least two transmitting antennas, it is characterized in that the method may further comprise the steps: A. The terminal performs channel estimation according to the common reference symbol sent by the base station, and obtains the state information of the downlink channel; B. The terminal determines, according to the state information of the downlink channel, the delay value used by each transmit antenna of itself during uplink cyclic delay diversity transmission; C. The terminal performs uplink transmission on each of its transmit antennas according to the delay value. 2. The method according to claim 1, wherein the state information of the downlink channel comprises a downlink channel transmission matrix, and step B comprises: B0. The terminal obtains an uplink channel transmission matrix by using the downlink channel transmission matrix, and the uplink channel transmission matrix is a transposition matrix of the downlink channel transmission matrix; B1. The terminal uses the uplink channel transmission matrix to determine the delay value used by each of its transmit antennas during uplink cyclic delay diversity transmission. 3. The method according to claim 2, wherein the terminal saves more than one delay value increment, and the uplink resource blocks used by the terminal use the same time delay diversity transmission in the uplink cycle. Delay value, then step B1 includes: For each delay value increment, determine the effective signal-to-noise ratio corresponding to the delay value increment, and the determination method is: for the subcarriers in each uplink resource block, use the maximum effective signal-to-noise ratio mapping The method, according to the delay value increment and the uplink channel transmission matrix, obtains the effective signal-to-noise ratio corresponding to the delay value increment; Select the delay value increment corresponding to the largest effective signal-to-noise ratio among the obtained effective signal-to-noise ratios, and determine the time delay used when each transmit antenna of the terminal performs cyclic delay diversity transmission according to the delay value increment value. 4. The method according to claim 2, wherein the terminal saves more than one delay value increment, and the uplink resource block used by the terminal uses different Delay value, then step B1 includes: For each uplink resource block, determine the delay value used when each transmit antenna of the terminal uses the uplink resource block to perform cyclic delay diversity transmission, and the determination method is as follows: For each delay value increment, for the subcarriers in the uplink resource block, use the maximum effective signal-to-noise ratio mapping method to obtain the delay value according to the delay value increment and the uplink channel transmission matrix The effective signal-to-noise ratio corresponding to the value increment; select the time delay value increment corresponding to the maximum effective signal-to-noise ratio in the obtained effective signal-to-noise ratio, and determine the use of each transmitting antenna of the terminal according to the time delay value increment The delay value used when the uplink resource block performs cyclic delay diversity transmission. 5. the method as claimed in claim 3 or 4, is characterized in that, step C comprises: The terminal uses the delay value to send the uplink data and the demodulated DM pilot for demodulating the data to the base station after cyclic delay diversity processing. 6. The method of claim 5, further comprising: The terminal uses the delay value to send the CQI pilot used for uplink channel quality indicator CQI estimation to the base station after cyclic delay diversity processing. 7. The method of claim 5, wherein the method further comprises: The terminal sends mutually orthogonal CQI pilots to the base station on each of its transmit antennas, and feeds back the time delay value to the base station. 8. A terminal for performing uplink multi-antenna transmission in a time division duplex TDD system, characterized in that the terminal is used for: Perform channel estimation according to the common reference symbol sent by the base station, and obtain the state information of the downlink channel; determine the time delay value used by each transmit antenna for uplink cyclic delay diversity transmission according to the state information of the downlink channel; According to the delay value, uplink transmission is performed on each transmit antenna. 9. The terminal according to claim 8, wherein the terminal comprises: The receiving unit is used to receive the common reference symbol sent by the base station, perform channel estimation according to the common reference symbol, and obtain the state information of the downlink channel; A determining unit, configured to determine a delay value used by each transmit antenna of the terminal during uplink cyclic delay diversity transmission according to the state information of the downlink channel; The transmission unit is configured to perform uplink transmission on each transmit antenna of the terminal according to the delay value. 10. The terminal according to claim 9, wherein the determining unit comprises: An uplink unit, configured to use the downlink channel transmission matrix in the downlink channel state information to obtain an uplink channel transmission matrix, where the uplink channel transmission matrix is a transposition matrix of the downlink channel transmission matrix; The delay value unit is configured to use the uplink channel transmission matrix to determine the delay value used by each transmit antenna of the terminal during uplink cyclic delay diversity transmission. 11. The terminal according to claim 10, wherein the delay value unit comprises: a storage unit for storing more than one delay value increment; The first calculation unit is configured to determine the delay value increment for each delay value increment when the uplink resource blocks used by the terminal use the same delay value during uplink cyclic delay diversity transmission. The effective signal-to-noise ratio corresponding to the quantity, the determination method is: for the subcarriers in each uplink resource block, using the maximum effective signal-to-noise ratio mapping method, according to the delay value increment and the uplink channel transmission matrix , to obtain the effective signal-to-noise ratio corresponding to the delay value increment; select the delay value increment corresponding to the largest effective signal-to-noise ratio among the obtained effective signal-to-noise ratios, and determine each time delay value of the terminal according to the delay value increment The delay value used when a transmitting antenna performs cyclic delay diversity transmission; The second calculation unit is configured to determine each transmission of the terminal for each uplink resource block when the uplink resource blocks used by the terminal use different delay values during uplink cyclic delay diversity transmission The delay value used when the antenna uses the uplink resource block to perform cyclic delay diversity transmission is determined by using the maximum effective The signal-to-noise ratio mapping method, according to the delay value increment and the uplink channel transmission matrix, obtains the effective signal-to-noise ratio corresponding to the delay value increment; Delay value increment, according to the delay value increment, determine the delay value used when each transmit antenna of the terminal uses the uplink resource block to perform cyclic delay diversity transmission. 12. The terminal according to claim 11, wherein the transmission unit is used for: Using the delay value, the uplink data and the demodulated DM pilot for demodulating the data are processed by cyclic delay diversity and then sent to the base station. 13. The terminal according to claim 12, wherein the transmission unit is also used for: Using the delay value, the CQI pilot used for uplink channel quality indicator CQI estimation is processed by cyclic delay diversity and sent to the base station. 14. The terminal according to claim 12, wherein the transmission unit is also used for: Send mutually orthogonal CQI pilots to the base station on each transmit antenna of the terminal, and feed back the time delay value to the base station.

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