CN1996782B - An Antenna Selection Indication Method for Space Adaptive Links - Google Patents

Abstract

The present invention discloses an antenna selection indication method for a space adaptive link, which includes the following steps: the transmitting end transposes the channel matrix obtained in the uplink as the estimation of the downlink channel matrix, and selects the antenna accordingly; The transmitting end jointly determines the pilot sequence sent by each transmitting antenna according to the antenna selection result and the corresponding relationship between the pilot frequency and the transmitting end antenna; the transmitter transmits the pilot sequence and the service signal after framing; the receiving end After receiving the signal from the transmitter, use the main and auxiliary frequency identifiers to match the main and auxiliary frequency with the received signal. The method of the present invention hides the antenna selection information in the multi-antenna pilots and sends them by means of pilot indications, so that the receiving end can judge which antenna signals carry information according to the pilot patterns, without consuming additional channel resources ; And the frequency signal is easy to identify, which satisfies the real-time requirements of fast-changing channels.

Description

An Antenna Selection Indication Method for Space Adaptive Links

technical field

The invention relates to a method for indicating antenna selection in a multiple-input multiple-output (MIMO) wireless communication system, in particular to a method for indicating antenna selection information in realizing adaptive space channel multiplexing.

Background technique

The proposal of multiple-input multiple-output (MIMO) technology has opened up a new field for modern wireless communication. It provides a future mobile communication system, especially for high-speed data access services, without increasing the bandwidth. It can greatly improve the means of system data rate and spectrum efficiency.

In the prior art, multiple antenna units are used at both the transmitting and receiving ends of a wireless system. Using the rich spatial multi-dimensional characteristics of the wireless scattering channel and working in a multi-input/multi-output mode, the system channel capacity can be improved dramatically. This is the basic idea of Multiple Input Multiple Output (MIMO) technology.

Multiple-input multiple-output MIMO systems take full advantage of the scatter-rich wireless channel between the transmitter and receiver. The characteristic of this channel is that the multiple data streams sent by the transmitting antenna array can have corresponding spatial characteristics to identify it on the side of the receiving antenna array, that is to say, different data streams have unique characteristics in the view of the receiving end. , Differentiable spatial characteristics, that is, the channel has multi-dimensional characteristics. And, in a slowly varying channel, it can be assumed that this spatial characteristic is constant in a specific time period. Therefore, a (M _T , _MR ) MIMO system can be understood in this way, that is, the MIMO channel can be regarded as composed of M=min(M _T , _MR ) parallel sub-channels, and the capacity of the entire MIMO channel is all The sum of subchannel capacities. Theoretically, since each sub-channel can have the same capacity limit, when the spatial characteristics of the receiving antenna segment between the transmitting antennas have good orthogonality, the capacity of the entire MIMO channel will increase the same capacity formula to a set The degree of surprise is shown in the formula C=M×B×log ₂ (1+ρ), where B is the signal bandwidth, and ρ is the average signal-to-noise ratio at the receiving end. The above formula shows that when the power and bandwidth are fixed, the maximum capacity or capacity upper limit of MIMO increases linearly with the increase of the minimum number of antennas.

The capacity of information theory has revealed that MIMO systems can obtain huge capacity, but how to approach or reach the theoretical capacity depends on the signal processing algorithm of the receiver. The MIMO channel in the mobile environment changes, and the capacity also changes. How the algorithm adapts to the changing channel is the key to realize the spatial adaptive link. Relevant studies have shown that it is not that the more transmit antennas, the greater the channel capacity in low-rank channels. The system capacity can be improved by selecting the transmitting antenna reasonably.

A more intuitive understanding is: in a low-rank channel, the signals sent by different antennas cannot be separated at the receiving end, or the cost of separation is very high, such as increased noise, requiring a higher signal-to-noise ratio. At this time, if all antennas Due to the mutual interference of the signals, the signals at the receiving end may not be recovered. In this case, if the transmitting antennas that can be separated at the receiving end are selectively selected for transmission, although the peak rate requirements cannot be met, it is still The link rate can be guaranteed to a certain extent. Therefore, it is necessary to determine the space division multiplexing channel and its number according to the characteristics of the channel and feed back the result to the transmitting end.

Among many airspace adaptive link methods, transmit antenna selection technology is a low-cost and low-complexity technology. This technology transmits different signals through different antennas, and realizes space division multiplexing by separating signals through multiple antennas at the receiving end. At this time, the channels corresponding to the antennas for transmitting service signals are space-division multiplexing channels, and the number thereof is the number of space-division multiplexing channels. Therefore, determining the space division multiplexing channel and its number according to the characteristics of the channel is to determine the antenna and its number for sending service signals.

How to determine the antenna and its number for sending service signals is a problem that needs to be considered by the antenna selection algorithm. There are many published methods, and how to select the antenna is not the focus of the present invention. Since the antenna selection algorithm is often completed at the receiving end, and the antenna selection operation is completed at the transmitting end, it is necessary to feed back the antenna selection information at the receiving end to the transmitting end.

Regarding the solution to the above problems, the methods disclosed in the prior art include:

In Chinese Patent Publication No. CN 1520063 "MIMO System, MIMO Receiver and Its Receiving Method", it is mentioned that the estimated channel state information is used to generate feedback information, and the feedback information is processed by compensating the feedback delay of the feedback path. However, its purpose is to use the feedback information to generate appropriate transmission weights. However, in an actual MIMO system, the feedback of channel state information requires a relatively large channel bandwidth.

In Chinese Patent Application No. 01137687.2, "Wireless System Feedback Technology with Multiple Transmitting and Receiving Antennas", the method of feedback rate indicator or gain indicator from the receiving end to the transmitting end is used to reduce the bandwidth of feedback channel state information, and the transmitter has Each data sub-stream adopts one-dimensional data encoding to ensure the reliability of indicator reception. However, channel coding the data stream will waste precious channel resources. Moreover, in order to ensure real-time performance, the return signal cannot be interleaved in the time domain for a long time, which further reduces the accuracy of the feedback signal.

A transmit antenna selector is described in Chinese Patent Publication No. CN 1578192 filed on July 8, 2004. The receiver performs BLAST decoding on the received signals from multiple receive antennas, and calculates the forward direction associated with each transmit antenna. The signal-to-noise ratio (SNR) of the channel is used to determine the channel characteristics of the forward channel corresponding to each transmitting antenna in the multiple transmitting antennas; and the channel state characteristics are fed back to the transmitter as the selection information of the transmitting antenna, and the transmitter according to This information selects a transmit antenna with a better status to transmit service signals. However, the specific feedback method is not specified in the patent.

There are many ways to indicate the selection result, for example, a dedicated byte can be used for indication. However, considering that the indicator signal requires higher accuracy than the service information, it is necessary to encode the indicator signal more reliably, which will waste precious channel resources. Moreover, in order to ensure real-time performance, the indicator signal cannot be interleaved in the time domain for a long time, which further reduces the accuracy of the indicator signal.

Therefore, the prior art still needs to be improved and developed.

Contents of the invention

The purpose of the present invention is to provide an antenna selection indication method for an airspace adaptive link. In the frequency division duplex FDD mode, since the channel state information from the transmitting antenna array to the receiving antenna array can only be obtained at the receiving end, no matter in what form the channel state information is fed back, the feedback link is essential, so a Feedback method for antenna selection information. In the time division duplex TDD system, due to the reciprocity of uplink and downlink, the channel from the transmitting antenna array to the receiving antenna array has a strong correlation with the channel from the receiving antenna array to the transmitting antenna array, which can be based on the uplink (downlink) link The channel characteristics of the downlink (uplink) channel are estimated. At this time, the antenna selection information only needs to be indicated and no feedback is needed, so the present invention proposes a method for indicating antenna selection information based on orthogonal pilot information.

Technical scheme of the present invention comprises:

An antenna selection indication method for a space adaptive link, comprising the steps of:

A. Design mutually orthogonal or quasi-orthogonal pilot sequences at the transmitter. Each transmitter antenna corresponds to two pilots, which are divided into main pilot and auxiliary frequency. The main pilot indicates that the transmitting antenna sends service signals, and the auxiliary frequency indicates that The transmitter antenna does not send service signals, and establishes a corresponding relationship between the pilot and the transmitter antenna;

B. The transmitting end transposes the channel matrix obtained in the uplink as an estimate of the downlink channel matrix, and selects the antenna of the transmitting end accordingly;

C. The transmitting end jointly determines the pilot sequence sent by each transmitting end antenna according to the selection result of the transmitting end antenna and the corresponding relationship between the pilot frequency and the transmitting end antenna;

D. The transmitter transmits the pilot sequence and the service signal after framing;

E. After receiving the signal sent by the transmitter, the receiving end uses the main and auxiliary frequency identifiers and the received signal to perform the main and auxiliary frequency matching, according to the situation of the main and auxiliary frequency and the correspondence between the pilot and the antenna of the transmitting end The situation judges the number of multiplexed signals in the signal received by the receiving end and the specific serial number of the transmitting end antenna, based on which it is judged which transmitting end antennas send service signals in the received signal and which transmitting end antennas do not send service signals.

The method described above, wherein, the step E also includes: after the main and auxiliary frequency identifiers perform the main and auxiliary frequency matching according to the received signal, select the antenna with a larger correlation value at each transmitting end, and the correlation value The larger one is the larger one of the main pilot correlation value and the secondary pilot correlation value of the antenna at the transmitting end.

The method, wherein, after the step E selects the antenna with a larger correlation value at each transmitting end, it also includes:

E1. Perform channel estimation according to the corresponding relationship between the pilot frequency and the antenna at the transmitting end;

E2. Mapping the antenna selection information of the transmitter according to the degree of correlation between the received signal and the main and auxiliary frequency matching;

E3. While performing antenna selection mapping at the transmitting end, the base station uses the received frame information to perform channel estimation, and uses the channel estimation matrix as an estimate of the channel matrix from the receiving end to the transmitting end, and performs antenna selection at the receiving end based on this estimation.

An antenna selection indication method for a space-adaptive link provided by the present invention uses the pilot indication to hide the antenna selection information in the multi-antenna pilots for transmission, so that the receiving end can judge which The signals of several antennas carry information, so that no additional channel resources are consumed; and the frequency signals are easy to identify, the accuracy of antenna selection information carried on the pilot frequency is very high, and it can better meet the real-time performance of antenna selection instructions Require.

Description of drawings

FIG. 1 is a schematic diagram showing an indication of transmit antenna selection information in Embodiment 1 of the method of the present invention;

FIG. 2 is a schematic diagram showing the indication of transmitting antenna selection information in Embodiment 2 of the method of the present invention.

Detailed ways

Various preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

The method of the invention provides an indication method for antenna selection information that does not need to be fed back in a space division multiplexing MIMO system, does not occupy extra channel bandwidth, has high accuracy, and can meet the real-time requirements of channel changes.

The technical content of the inventive method comprises the following steps:

Step 1: Design mutually orthogonal pilot sequences at the transmitter. Each transmitter antenna corresponds to two pilots, which are divided into main pilot and auxiliary pilot. The main pilot corresponds to the transmitting antenna to send service signals, and the auxiliary pilot corresponds to the transmitting end. The antenna does not send service signals; establish the corresponding relationship between the pilot and the antenna of the transmitting end.

Step 2: The transmitting end transposes the channel matrix obtained in the uplink as an estimate of the downlink channel matrix, and selects the antenna of the transmitting end accordingly.

Step 3: The transmitting end jointly determines the pilot sequence sent by each transmitting end antenna according to the selection result of the transmitting end antenna and the corresponding relationship between the pilot frequency and the transmitting end antenna.

Step 4: The transmitting end frames the pilot sequence and service signals and transmits them.

Step 5: After receiving the signal from the transmitter, the receiving end uses the main and auxiliary frequency identifiers to match the main and auxiliary frequency with the received signal, according to the situation of the main and auxiliary frequency and the corresponding situation between the pilot and the antenna of the transmitting end Judging the number of multiplexed signals (that is, space division multiplexing coefficient) and the specific serial number of the transmitting antenna in the signal received by the receiving end, based on which it is judged which business signals sent by the transmitting antenna are included in the received signal, and which are not included The service signal sent by the transmitter antenna.

The following uses an example in which the base station and the mobile station antennas are configured as 4x4 to illustrate the specific implementation process of the antenna selection information feedback method.

First, the design method of the pilot frequency of the present invention is explained: the following design is only to explain the idea and principle of the invention, but the scope of the invention is not limited to specific examples and conditions, such as the length of the pilot frequency, orthogonal sequence and scrambling code selection etc.

The orthogonal sequence adopts the complex Walsh sequence, and the large M sequence is used for scrambling. The Walsh sequence is as follows:

W11+i -1-i 1+i -1-i 1+i -1-i 1+i -1-i

W21-i 1-i 1-i 1-i 1-i 1-i 1-i 1-i

W31+i -1-i -1-i 1+i 1+i -1-i -1-i 1+i

W41-i 1-i -1+i -1+i 1-i 1-i -1+i -1+i

W51+i -1-i 1+i -1-i -1-i 1+i -1-i 1+i

W61-i 1-i 1-i 1-i -1+i -1+i -1+i -1+i

W71+i -1-i -1-i 1+i -1-i 1+i 1+i -1-i

W81-i 1-i -1+i -1+i -1+i -1+i 1-i 1-i

The Walsh sequence constitutes the pilot sequence Pi after scrambling, 1≤i≤8. For the i-th array element, the dominant frequency is Pi, and the auxiliary frequency is P(i+4). Pi has the following characteristics: Pi and Pj are orthogonal, and i≠j.

Establishing the above correspondence between the antenna and the pilot pattern has two functions. First, the receiving end determines the sequence of elements in the channel matrix based on this; secondly, the receiving end determines which antennas send service signals and which antennas do not include service signals sent by the received signal based on this. For example, the main pilot pattern indicates that the service signal sent by its corresponding antenna is received, and the auxiliary pilot pattern indicates that there is no service signal sent by its corresponding antenna in the received signal.

By observing the pilot pattern, it can be found that the first 4 symbols of the main pilot and the auxiliary pilot of each array element are the same, and the signs of the last 4 symbols are opposite. Such a design is to reduce the calculation amount when judging the pilot pattern. Taking pilot No. 1 and No. 5 as examples, the first 4 symbols and the last 4 symbols of pilot P1 are used to correlate with the corresponding received signals, and the sum and difference of the two correlation coefficients can be obtained at the same time. The correlation coefficient between the No. 1 pilot and No. 5 pilot and the received signal can be judged as the main pilot or the auxiliary pilot according to the magnitude of the correlation coefficient modulus, without requiring two correlation operations with a length of 8.

The above-mentioned pilot design is applicable to both the base station and the mobile station. After the pilot frequency design is completed, the antenna selection result can be indicated according to the main pilot frequency transmitted by the antenna.

The pilot sequence selection method and framing method of the transmitting antenna will be described below.

As shown in FIG. 1 , a schematic diagram of the processing flow of the antenna selection information indication is given. In the figure, the front part of the frame is the pilot part, and the back part is the service signal part. Regardless of the antenna selection result, the pilot signals of the four antennas are always being sent to facilitate channel estimation.

Since the signals sent by the multiple antennas of the base station carry mutually orthogonal pilot information, and many known methods can be used for channel estimation, the method of the present invention can obtain the channel information from the base station to the mobile station of the MIMO system, and then obtain the channel Matrix. Since in the TDD mode, the uplink channel information and the downlink channel information have a strong correlation when the interval between the receiving time slot and the sending time slot is very short, so the transposition of the channel matrix from the base station to the mobile station can be used as the Estimation of the channel matrix of the base station.

After the downlink channel matrix is obtained, a known antenna selection algorithm can be used for antenna selection. Assuming that the mobile station thinks that the third antenna in this frame does not transmit service data, and other antennas transmit service data, then its pilot design is as follows: according to the order of 1 to 4 antennas, the pilots are: P1, P2, P7, P4, at this time The multiplexing factor is 3, and 1, 2, and 4 antennas transmit service data. The selected pilot frequency is framed and sent with the service signal in the manner shown in FIG. 1 .

After the base station receives the signal sent by the mobile station, the master pilot frequency recognizer performs master pilot frequency matching according to the received signal, and selects the one with the larger correlation value of each transmitting end antenna, and the one with the larger correlation value is the transmitting end antenna The larger one of the dominant frequency correlation value and the secondary frequency correlation value. According to the above-mentioned pilot transmission situation of the mobile station, it should be that the P1, P2, P7, and P4 pilots get the maximum value. Firstly, the channel estimation is performed according to the corresponding relationship between the pilot frequency and the antenna of the mobile station. That is, the correlation value of P1 corresponds to the channel response of the mobile station antenna 1, and the correlation values of P2, P7 to P4 correspond to the channel responses of the mobile station antennas 2 to 4, respectively. Next, the mapping of antenna selection information is performed. That is, a higher correlation value of P1 than a correlation value of P5 indicates that antenna 1 of the mobile station transmits the main pilot information, and therefore, the received signal includes service data of the first antenna of the mobile station. The correlation value of P7 is higher than the correlation value of P3, indicating that antenna 3 of the mobile station has sent pilot frequency information, therefore, the received signal does not include the service data of the third antenna of the mobile station. Others and so on.

While performing antenna selection mapping, the base station uses the received frame information to perform channel estimation, and uses the channel estimation matrix as an estimation of the channel matrix from the base station to the mobile station, and performs antenna selection based on this estimation. Assume that the antenna selection result at the base station is that the second antenna does not transmit signals, and other antennas transmit signals. Then the pilot frequency design is as follows: according to the order of 1 to 4 antennas, the pilot frequency is: P1, P6, P3, P4. At this time, the multiplexing factor is 3, and the first, third, and fourth antennas transmit service data. The selected pilot frequency is framed and sent with the service signal in the manner shown in FIG. 1 .

From this point of view, after receiving the pilot information from the base station (mobile station), the mobile station (base station) knows which antennas in the current frame signal carry service signals. The pilot frequency of this method indicates that the current frame is valid, which avoids a frame-long time delay caused by the feedback link, which is beneficial to systems with rapidly changing channels, and is suitable for systems with different transceiver antennas.

Next, the antenna configuration 4x2 of the base station and the mobile station is taken as an example to illustrate the specific implementation process of the antenna selection information feedback method.

In terms of pilot design, the method in Embodiment 1 can still be used. However, the corresponding relationship between the pilot pattern and the antenna is stipulated as follows:

At the base station, Pi and P(i+4) correspond to the i-th array element (1≤i≤4) of the base station, and at the mobile station, Pi and P(i+4) correspond to the i-th array element of the mobile station (1 ≤i≤2).

The pilot sequence selection method and framing method of the transmitting antenna will be described below, and FIG. 2 shows a schematic diagram of the processing flow indicated by the antenna selection information. The frame structure in the figure is similar to the first embodiment.

On the mobile station side, the received frame information is used for channel estimation, and the channel estimation matrix is used as the estimation of the channel matrix from the mobile station to the base station, and the antenna is selected according to this estimation. Assume that the mobile station thinks that the second antenna sends a signal, but the first antenna does not send a signal. Then the pilot frequency design is as follows: according to the order of 1 to 2 antennas, the pilot frequency is: P5, P2. At this time, the multiplexing factor is 1, and the second antenna transmits service data. The selected pilot frequency is framed and sent with the service signal in the manner shown in FIG. 2 .

After the base station receives the signal sent by the mobile station, the main and auxiliary frequency identifiers perform the main and auxiliary frequency matching according to the received signal, and select the one with the larger correlation value of each transmitting end antenna, and the one with the larger correlation value is the transmitting end The larger of the main pilot correlation value and the pilot pilot correlation value of the antenna. According to the pilot transmission situation of the above mobile station, the P5 and P2 pilots should get the maximum value. First, the channel is carried out according to the corresponding relationship between the pilot frequency and the mobile station antenna Estimation. That is, the correlation value of P5 corresponds to the channel response of antenna 1 of the mobile station, and the correlation value of P2 corresponds to the channel response of antenna 2 of the mobile station. Secondly, the antenna selection information mapping is performed. That is, the correlation value of P2 is higher than that of P6, indicating that , the mobile station antenna 2 has sent the main pilot information, therefore, the received signal contains the service data of the second antenna of the mobile station. The correlation value of P5 is higher than that of P1, indicating that the mobile station antenna 1 has sent the pilot pilot information, therefore, The received signal does not contain the service data of the first antenna of the mobile station.

While performing antenna selection mapping, the base station uses the received frame information to perform channel estimation, and uses the channel estimation matrix as an estimation of the channel matrix from the base station to the mobile station, and performs antenna selection based on this estimation. Assume that the antenna selection result at the base station is that the second and third antennas do not transmit signals, and the other antennas transmit signals. Then the pilot frequency design is as follows: according to the order of 1 to 4 antennas, the pilot frequency is: P1, P6, P7, P4. At this time, the multiplexing factor is 2, and the first and fourth antennas transmit service data. The selected pilot frequency is framed and sent with the service signal in the manner shown in FIG. 2 .

The method of the present invention realizes the transmission of antenna selection information by means of pilot frequency indication, that is, the antenna selection information is hidden in the pilot frequency of multiple antennas and sent, and the receiving end can judge which antenna signals carry information according to the pilot frequency pattern. Since in the MIMO system, multiple antennas need to transmit different pilots for channel estimation, therefore, no additional channel resources need to be consumed. Moreover, since the pilot frequency is often the basis for communication establishment, the pilot signal is often strong and easy to identify, and the recovery accuracy of the antenna selection information carried on the pilot frequency is very high. At the same time, the pilot information is often extracted frame by frame, which can better meet the real-time requirements.

It should be understood that the above descriptions for specific embodiments are relatively detailed, but should not be considered as limiting the scope of the patent protection of the present invention, and the scope of protection of the patent protection of the present invention should be determined by the appended claims.

Claims (3)

1. An antenna selection indication method for a space adaptive link, comprising the steps of: A. Design mutually orthogonal or quasi-orthogonal pilot sequences at the transmitter. Each transmitter antenna corresponds to two pilots, which are divided into main pilot and auxiliary frequency. The main pilot indicates that the transmitting antenna sends service signals, and the auxiliary frequency indicates that The transmitter antenna does not send service signals, and establishes a corresponding relationship between the pilot and the transmitter antenna; B. The transmitting end transposes the channel matrix obtained in the uplink as an estimate of the downlink channel matrix, and selects the antenna of the transmitting end accordingly; C. The transmitting end jointly determines the pilot sequence sent by each transmitting end antenna according to the selection result of the transmitting end antenna and the corresponding relationship between the pilot frequency and the transmitting end antenna; D. The transmitter transmits the pilot sequence and the service signal after framing; E. After receiving the signal sent by the transmitter, the receiving end uses the main and auxiliary frequency identifiers and the received signal to perform the main and auxiliary frequency matching, according to the situation of the main and auxiliary frequency and the correspondence between the pilot and the antenna of the transmitting end The situation judges the number of multiplexed signals in the signal received by the receiving end and the specific serial number of the transmitting end antenna, based on which it is judged which transmitting end antennas send service signals in the received signal and which transmitting end antennas do not send service signals. 2. The method according to claim 1, characterized in that, said step E also includes; after said main and auxiliary frequency identifiers perform main and auxiliary frequency matching according to the received signal, select each transmitter antenna correlation The larger the value, the larger the correlation value is the larger of the main pilot correlation value and the secondary pilot correlation value of the antenna at the transmitting end. 3. The method according to claim 2, characterized in that, after the step E selects the larger one of each transmitter antenna correlation value, it also includes: E1. Perform channel estimation according to the corresponding relationship between the pilot frequency and the antenna at the transmitting end; E2. Mapping the antenna selection information of the transmitter according to the degree of correlation between the received signal and the main and auxiliary frequency matching; E3. While performing antenna selection mapping at the transmitting end, the base station uses the received frame information to perform channel estimation, and uses the channel estimation matrix as an estimate of the channel matrix from the receiving end to the transmitting end, and performs antenna selection at the receiving end based on this estimation.

Images