WO2004013988A1

WO2004013988A1 - A transmitting antenna select methods in multi-antennas communication environment and transmitting and receiving methods of the signal

Info

Publication number: WO2004013988A1
Application number: PCT/CN2003/000628
Authority: WO
Inventors: Lei Zhou; Lixin Sun; Yuehua Chen; Zhibin Zheng
Original assignee: Huawei Technologies Co., Ltd
Priority date: 2002-08-05
Filing date: 2003-08-05
Publication date: 2004-02-12
Also published as: AU2003255091A1

Abstract

The present invention discloses a kind of select methods of transmitting antennas in multi-antennas communication environment. In the methods, the signal transmitting terminal first transmits a pilot on all of the antennas, the signal receiving terminal measure channel estimate, which obtained from different receiving antennas and came from every transmitting antennas of the signal transmitting terminal. The signal receiving terminal then select one or more antennas as the transmitting antennas from multi-antennas of the signal transmitting terminal, on the basis of size of Signal Noise Ratio measured by the receiving channel. When select one antenna, the selected result would be directly notified the signal transmitting terminal. Or else, the signal receiving terminal estimate a relativity between the spatial vector with one another, still on the basis of the channel spatial vector obtained from all of the receiving antennas. According to the relativity, select one or more antennas as the transmitting antennas from multi-antennas of the signal transmitting terminal, the selected result then would be notified to the signal transmitting terminal. The present invention also provides a signal transmitting and receiving method, which utilizes aforementioned methods and based upon time division duplexing mode.

Description

Method for selecting transmitting antenna in multi-antenna environment and method for transmitting and receiving signal

The invention relates to a method for selecting a transmitting antenna in a wireless multi-antenna communication system and a method for transmitting and receiving signals.

Background technique

Wireless communication provides a means for people to connect with each other and obtain information anytime, anywhere, so it has gained rapid popularity in recent years. However, in the current wireless environment, due to mobile requirements, there are certain restrictions on the directional transmission of wireless signals, so that the wireless communications of different users inevitably interfere with each other. In order to ensure the normal performance of various wireless communications, the use of wireless spectrum is generally strictly restricted and managed. In this way, wireless communications cannot have as much bandwidth as wired communications. Therefore, based on the limited available wireless spectrum, how can Increasing the information transmission capacity of wireless communication systems is an urgent problem that needs to be solved.

In wireless communication, fading wireless channels are one of the main factors hindering effective communication. To this end, researchers have proposed a multi-antenna transmit / receive technique, "GJ Foschini," Layered space-t ime archi tecture for wireless communicat ion in fading environment When us ing mul ti-element antennas ", Bel 1 Labs Technical Journal, pp. 41-59, Autumn 1996.), the above technology is disclosed. This technology can ensure high efficiency under the independent flat fading channel. height of High-speed data transmission communication. However, due to the influence of mutual interference in wireless communication, the signal-to-interference (noise) ratio of multi-antenna reception is not very high; In addition, the multiple channels of wireless reception cannot be kept independent of each other at any time, in each unit time of reception In addition, there is still a large interference between each other, coupled with factors such as mutual coupling of antennas, the simultaneous transmission / reception method of multiple antennas still has the problem that the efficiency is severely reduced. At present, research on multi-antenna systems has begun to consider how to select the transmitting antenna based on feedback, such as "optimal antenna selection for multi-input multiple-output systems using space-time block coding" (A Paulra j and D Gore, " Opt imal antenna select ion in MIMO sys tems wi th space-t ime block coding ", IEICE Trans. Commun., 200KE84-B): 7, pp. 1713-1717. However, there must be a delay in any feedback, and the existence of the delay will affect the efficiency of the system. Therefore, in a multi-antenna communication environment, properly selecting a transmitting antenna can reduce mutual interference of transmitted signals, improve signal energy transmission efficiency, and make receiving processing simple. Summary of the invention

In order to solve the problem of transmitting antenna selection, the present invention provides a method for selecting a transmitting antenna in a multi-antenna communication environment. Using the transmitting antenna selected by the method to perform signal transmission can reduce mutual interference of transmitting signals and improve signal energy transmission efficiency. At the same time, it can also make the reception processing of the signal simpler;

At the same time, in order to improve the signal energy transmission efficiency, the present invention also provides a method for transmitting and receiving signals based on the time division duplex mode using the antenna selection method described above. Using this method can improve the transmission efficiency of high-speed data, and The end obtains the highest possible signal-to-interference (noise) ratio. Based on the above requirements, the method for selecting a transmitting antenna in a multi-antenna communication environment provided by the present invention includes the following steps:

Multiple antennas are set at the signal transmitting end and the signal receiving end respectively;

The signal transmitting end first transmits pilots on all antennas, and the signal receiving end measures the channel estimates of each transmitting antenna of the signal transmitting end obtained on different receiving antennas;

The signal receiving end selects one or more antennas from the multiple antennas of the signal transmitting end as the transmitting antennas according to the measured signal-to-noise ratio of the receiving channel. If one is selected, the selection result is notified to the signal transmitting end; otherwise, the signal receiving end The channel space vectors obtained on all receiving antennas are used to calculate the correlation between the space vectors. Based on the correlation, one or more of the multiple antennas at the signal transmitting end are selected as the transmitting antennas, and the selection result is notified to the signal transmitting end. ;

The signal transmitting end selects a transmitting antenna according to the selection result of the signal receiving end.

The correlation between the calculated space vectors is completed according to the following formula:

Wherein, for the first _Z 'transmit antenna spatial channel column vectors of the first / transmit antenna channel spatial column correlation coefficient vector, ^ representative complex column vector of the conjugation transpose, ^ representative complex column vector conjugation The transpose represents the modulus of taking a complex number.

The transmitting antenna is selected according to the principle of minimum correlation of the channel space vector and the square and maximum of the modulus of each element of the channel space vector.

When the method is implemented based on a time division duplex system, the signal transmitting end is a base station and the signal receiving end is a mobile station. The mobile station then determines the channel conditions of the uplink and downlink multi-antennas at the same time according to the pilot of the base station to directly select the uplink transmitting antenna. A method for transmitting and receiving a signal based on a time division duplex mode by using the foregoing transmitting antenna selection method provided by the present invention includes:

Step 1: All antennas of the base station transmit pilot signals within a fixed allocated time period; Step 2: The mobile station measures all received pilot signals on its different receiving antennas, and selects one or more antennas, As an uplink transmitting antenna, since the next uplink transmitting moment, the selected antenna is used as a transmitting antenna to transmit signals in the uplink transmitting time period. Step 3: The mobile station receives all received pilot signals on its different antennas. Selecting one or more antennas of the base station as a transmitting antenna, and notifying the base station to use the antenna selected by the mobile station to transmit a signal to the mobile station in the next downlink transmission;

Step 4: The base station uses multiple antennas to receive signals from the mobile station, and according to the mobile station's notification, selects one or more antennas as the downlink transmitting antennas, and sends the signals to the mobile station within the downlink transmitting time period from the next downlink transmission time. transmit a signal.

In step 1, all antennas of the base station transmit pilot signals in a code division manner within a fixed allocated time period.

In the pilot signal transmission according to the code division mode, all antennas of the base station select a code obtained by different cyclic shifting of the same code as a pilot for transmission within a fixed allocated time period.

In step 1, all antennas of the base station transmit pilot signals in a time-division manner within a fixed allocated time period.

The one or more antennas selected in step 1 are all antennas with the greatest received signal strength or the sum of the signal-to-noise ratio. The one or more antennas selected in step 3 are the antennas with the largest received signal strength or the sum of the signal-to-noise ratio of the transmitted signals on all mobile station antennas.

Another method for transmitting and receiving signals based on a time division duplex mode using the above-mentioned transmitting antenna selection method provided by the present invention includes:

Step 11: The mobile station measures the received signals on different receiving antennas on the local side, selects one of the antennas as an uplink transmitting antenna, and uses the selected antenna as a transmitting antenna at the next uplink transmitting moment, and transmits the signal at the uplink transmitting time. Transmit signal within the segment;

Step 12: The base station selects one of the antennas as a downlink transmitting antenna based on the signals of the mobile station received on the multiple antennas on the local side, and transmits a signal to the mobile station within the downlink transmitting time period at the next downlink transmission time.

The received signals on the different antennas measured by the mobile station in step 11 are pilot signals transmitted by the base station, broadcast signals transmitted by the base station, or dedicated channel signals transmitted by the base station to the mobile station.

One of the antennas selected in steps 11 and 12 is the antenna with the highest received signal strength or signal-to-noise ratio.

When the base station transmits signals in step 12, if the channels of the multiple antenna signals on the base station side are strongly correlated, the multiple antennas on the base station side are selected to transmit the same signal, and the different antennas are weighted to achieve the orientation of the signals. emission.

The method of the present invention selects the transmitting antenna of the signal transmitting end through the signal receiving end, so that the signal transmitting end transmits the signal through the selected antenna, so that high-speed data transmission can be implemented more effectively, and the interference of concurrent data streams with each other can be reduced; The premise of the realization of the existing multi-antenna transmitting / receiving method is the spatial direction formed by each transmitting signal on the multi-receiving antenna. The correlation between the quantities is small. Due to the randomness of the charging channel, this condition is not always met. However, when all the channels of the transmitted signals have a large correlation, the channels experienced by some of the signals may still be orthogonal to each other, or the correlation is small. Therefore, the signal receiving end of the present invention can obtain a more efficient signal transmission by selecting a part of the transmitting antenna according to the measured signal-to-noise ratio of the receiving channel and the correlation between the channel space vectors of the signal. Can make the receiving process of the signal simpler.

In a wireless cellular communication environment, the achievable signal-to-noise ratio is generally low due to the presence of large interference. In the method of the present invention, high-speed transmission can be performed by selecting a small number of transmitting antennas to avoid interference caused by other transmitting antennas. For signals on different transmitting antennas, the probability that the channels have a small correlation with each other is the same. Therefore, the present invention can obtain an effective and reasonable application of multi-antenna transmission by selecting based on the correlation of channel space vectors, which is more conducive to Improved efficiency of wireless cellular communication systems.

Compared with the existing multi-antenna transmitting / receiving method, the signal transmitting and receiving method provided by the present invention can be applied under the condition that multiple signal channels are independent of each other, and also can be used only when the noise signals of different antennas are independent of each other. It can be used in a wider range of practical environments, and can be used in both diversity antennas and smart antennas. In addition, the present invention uses the broadcast of a multi-antenna common pilot signal of a base station, so that a mobile station can simultaneously estimate the The channel between multiple antennas is based on this. Therefore, in a time division duplex system, the mobile station can obtain the uplink and downlink channel conditions at the same time, so that the optimal uplink transmitting antenna can be selected according to a certain principle. Or multiple transmitting antennas, while transmitting data in the uplink, notify the base station of the transmission that should be selected next time when transmitting data for the mobile station Antenna, so as to obtain the optimized performance of uplink and downlink multi-antenna transmission and reception at the same time; therefore, using this method can improve the transmission efficiency of high-speed data and obtain the highest signal-to-interference (noise) ratio at the signal receiving end. ·

If the antenna single transmission and multiple reception methods are used to transmit and receive wireless signals, since multiple signal channels are not required to be independent of each other, the practical environment can be more extensive, and it can be used in both diversity antennas and smart antennas. . At the same time, because single-antenna transmission is used, the mutual interference of the transmitted signals is reduced. Not only the receiving and processing tube is single, the highest possible signal-to-interference (noise) ratio can be obtained, but also the signal energy transmission efficiency is higher, so it is more suitable for wireless environments. application. In addition, a single antenna is used for transmission, and there is no need to synchronize the signals of multiple transmitting antennas on the receiving antenna, which is easier to implement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example diagram of a multi-antenna time division duplex system to which the present invention is applied;

FIG. 2 is a flowchart of an embodiment of a transmitting antenna selection method according to the present invention; and FIG. 3 is a schematic diagram of uplink and downlink transmission period allocation.

detailed description

In the existing multi-antenna system, the premise of its application is the existence of independent Rayleigh fading channels. Assume that the multi-antenna transmitting / receiving environment shown in FIG. 1 is adopted, the number of transmitting antennas in the figure is 4, and the receiving is 6 antennas. During actual reception, it is assumed that the channel does not change or changes slowly during a processing cycle. Therefore, on the 6 ^^ receiving antenna, you can get 24 constant or slowly changing channels:

Among them, ½ represents the channel experienced by the transmitted signal of the / th base station antenna to reach the mobile station antenna of the žth base station, i ≤ ⁶ , i <y <4 _o , and i ≤ ≤ ⁴ are corresponding vector representations. For this processing period, since the channel becomes some constants that are basically constant, there are no mutually independent conditions. At the mobile station, the signals it receives are:

(2)

Among them, l ≤ z '≤ ⁶ are the received signals on different receiving antennas, 1 ≤ ≤ ⁴ are the four transmitted signals on the transmitting antenna, and nl <i <6 is the noise on each receiving antenna. Formula (2) shows that the four transmit signals are spatially encoded on the six receiving antennas, and the encoded spatial codes are vectors, 1 ≤ '≤ ⁴ . Therefore, the most efficient reception of formula (2) occurs if and only if the above-mentioned spatial codes are orthogonal to each other, or the correlation coefficient is small. When there is a strong correlation between different space codes, the performance of the above-mentioned multi-antenna transmission / reception system will inevitably decrease.

According to the above analysis, according to the degree of linear correlation of different channel vectors k, ≤j≤4, one or more antennas are selected for transmission, and then multiple antennas are used for reception at the receiver, so as to obtain as orthogonal as possible in space. Multiple transmission signals can simplify the receiving process and effectively improve the performance of signal transmission. The implementation of the transmitting antenna selection method according to the present invention is described in further detail below with reference to FIG. 1.

FIG. 2 is a flowchart of an embodiment of the method according to the present invention. According to FIG. 2, firstly, multiple antennas need to be set on the signal transmitting end and the signal receiving end respectively. The signal transmitting end first transmits pilots on all antennas through step 1. The signal receiving end measures each transmission of the signal transmitting end obtained on different receiving antennas. Antenna channel estimation, and then the signal receiving end in step 2 according to the estimated signal-to-noise ratio measured from the receiving channel, select one or more of them as the transmitting antenna from multiple antennas at the transmitting end of the signal, for example, select the transmitting signal at The antenna with the largest sum of signal-to-noise ratios on all mobile station antennas. Generally, when the signal-to-noise ratio is better, the number of antennas selected is larger. Then, in step 3, it is determined that several antennas are selected in step 2. If one is selected, the signal receiving end notifies the signal transmitting end of the selection result in step 5, and the signal transmitting end selects the transmitting antenna according to the selection result of the signal receiving end. If it is learned through step 3 that more than two antennas are selected, the signal receiving end resides on the channel space vectors obtained on all the receiving antennas in step 4 and calculates the correlation between the space vectors. Among the multiple antennas on the transmitting end, one or more antennas are selected as the transmitting antennas, and then the signal receiving end informs the signal transmitting end of the selection result in step 5, and the signal transmitting end selects the transmitting antenna according to the selection result of the signal receiving end.

The calculation of the correlation between the space vectors in step 4 is performed according to the following formula:

Where is the correlation coefficient between the channel space column vector of the first transmitting antenna and the channel space column vector of the / th transmitting antenna, which represents the conjugate transpose of the complex number vector, and the conjugate transpose of the complex number vector, l Represents the modulus of taking a complex number. In step 4, the transmitting antenna is selected according to the principle of minimum correlation of the channel space vector and maximum sum of squares of the moduli of the elements of the channel space vector.

For example, when the receiving end estimates that the channel is as follows:

Then we can know by calculation, c ₁₂ = c ₂₃ = 0, c ₁₃ = l, c ₁₄ = c ₂₄ = c ₃₄ = 0.707. The channel space vector of the signal of the transmitting antenna 1 is completely related to the channel space vector of the signal of the transmitting antenna 3. The signal strength of the transmitting antenna 1 is higher than the signal strength of the antenna 3, and the channel space vector of the signal of the transmitting antenna 4 is any other The channel space vectors of the signals all have a strong correlation. Therefore, selecting the transmitting antennas 1 and 2 to transmit signals respectively can achieve the most effective signal transmission.

The method described in FIG. 2 can be applied to a frequency division duplex (FDD) mode and a time division duplex (TDD) mode. When the method described in FIG. 2 is implemented based on a time division duplex system, a signal transmitting end is a base station and a signal receiving end is mobile. According to the pilot of the base station, the mobile station can simultaneously determine the channel conditions of the uplink and downlink multi-antennas so as to directly select the uplink transmitting antenna. The selection of the uplink transmitting antenna described here is to select the one or more antennas that have the greatest received signal strength or the sum of the signal-to-noise ratio.

The key to the realization of a multi-antenna system is the production of multi-antennas at one end of the mobile station. The difficulty lies in the contradiction between the portability of the device and the multi-antenna channels. Due to the diversity of the actual environment, when the receiving antennas of a mobile station are half the carrier wavelength, There is still a possibility that there is a large correlation between the fading channels, which makes it difficult to set the antenna of the mobile station. However, with regard to noise, since the azimuth distribution of the incoming signal of the noise signal is relatively broad, and the noise itself is also a combination of multiple signals, implementing multiple antennas on a mobile station to receive noise independently of each other is better than ensuring the signals on different antennas. It is easier to implement independent channels.

Taking two receiving antennas as an example, when the noises they receive are independent of each other, for the signals transmitted by a single transmitting antenna, the received signals on the two receiving antennas can be expressed by the following expressions:

.

Where and are the received signals on antennas 1 and 2, respectively, and ^ is the symbol transmitted by a single antenna. Assuming that the symbol energy is, / and ^ are the fading channels that the symbol experiences when it reaches the two receiving antennas, respectively. ! And "2" are the noise received by the two antennas.

According to the existing method of transmitting and receiving wireless signals with multiple antennas, it is assumed that A ₂ and A ₂ are known (or estimated) flat fading channels, and are unchanged or slowly changed within a short period of signal reception (this is not required here The two channels are independent of each other), and it is assumed that the noises "1 and" · 2 received by the two antennas are Gaussian noise and the noise power is σ ² . As can be seen from the previous discussion, it is easy to ensure that these two noise signals are independent of each other in implementation. For example, when two antennas are separated by more than half of the carrier wavelength, the two noise signals are independent of each other. Perform the maximum ratio combining of the received signals of the antennas, then the combined signals:

r

(h * _l n ₁ + h ₂ * n ₂ ) (4)

The resulting signal-to-noise ratio is:

It turns out that the signal-to-noise ratios of the two ^^ receiving antennas are ¹ ^ ² ^, ^ ^{2 | 2} ^, and it can be known from the formula (5) that the signal-to-noise ratio of the received signal is enhanced. Because the enhancement of the signal-to-noise ratio does not require independent signal channel components, but only the condition that the noise is independent of each other; this condition is easily satisfied in a wireless environment. For example, when setting multiple antennas, as long as the distance between different antennas exceeds the carrier Half of the wavelength can be basically satisfied, whether on the base station side or the mobile terminal side.

In the time division duplex system, the same carrier is used for the uplink and the downlink. Therefore, the channel estimates on both sides can be obtained at the same time through single-sided channel measurement. This makes the multi-antenna system simplify the feedback of the channel measurement when it is applied in the time division duplex system, which is beneficial to improve the performance of the multi-antenna transmission / reception method.

Unlike a base station broadcasting a pilot signal, in a wireless communication cell, it is impossible for a mobile user to send a pilot signal to the base station at any time for the base station to measure the channel conditions of the user. This is particularly prominent when multi-antenna transmission / reception is implemented. Assume that there are three users in a cell, and each user's mobile device has two transmit antennas. In order for the base station to obtain an effective estimate of the transmission channel conditions of all antennas of these user equipments, these users need to be allocated 3 2 = 6 resources. In a code division multiple access system, it means that 6 codes need to be allocated. In a time division multiple access system, Medium means that 6 timeslots long enough need to be allocated, and the number of resources to be allocated increases linearly with the number of users. Therefore, in a general time division duplex wireless communication system, only a method in which a base station broadcasts a pilot signal, that is, a common pilot signal, can be adopted, so that a mobile station can obtain uplink and downlink channel estimates through measurement. In a multi-antenna transmitting / receiving system with a selection of transmitting antennas, applying the above-mentioned method of unidirectional common pilot signal transmission will cause signal transmission in a certain direction to lack a basis for judgment because it does not have the channel estimation of all antennas. As a result, the performance of the method is partially lost, so the above drawbacks must be avoided in a multi-antenna transmission / reception system.

The implementation of the signal transmission and reception method based on the time division duplex mode provided by the present invention is described below.

In a time division duplex based wireless communication system, multiple antennas are first set on the base station side and the mobile station side respectively. The multiple antennas are set according to the principle that the noise received by each antenna is independent of each other. Specifically, the following methods can be used to set: The distance between the antennas on the side can be determined according to the sector angle of the service, so that the distance between two adjacent antennas is not less than the load.

I © AO

Half-wavelength x 360 degrees / α, that is, the distance between adjacent antennas is greater than or equal to "^^ ² ^; it can also be set to half of the carrier wavelength; the distance between adjacent antennas on the side of the mobile station should not be less than the carrier Half the wavelength, that is, the distance between adjacent antennas is greater than or equal to. For the above-mentioned antenna settings, further requirements can be made so that the channels experienced by each signal received on different antennas are independent of each other, that is, the above Multiple antennas are set up according to the principle that the channels of signals from different transmitting antennas reach different receiving antennas are independent of each other.

In a time division duplex system, separate time slices are arranged in the time period of downlink transmission for all transmitting antennas of the base station to transmit a common pilot. The transmission mode of the pilot signals of different antennas may be code division or time division. If the code division method is adopted, all antennas of the base station may also select codes obtained by different cyclic shifts of the same code as pilots for transmission within a fixed allocated time period. For example, if there is a code sequence [mi m ₂ … _1M ], a pilot sequence can be assigned to the base station antenna 1 [mi… m _m mi… m _s ], base station antenna 2 assigns pilot sequence

[ ₉ … w ₁₂₈ "… ₁₆ ], and so on. All codes obtained by one code cyclic shift have better properties, that is, the channel estimation is extremely simple, as long as the same sequence is used for multiple round multiplication, All channel estimates can be obtained. When multi-antenna common pilot transmission, the use of this code is very helpful for the realization of channel estimation for a mobile phone that can be simplified. The mobile station can measure itself based on the common pilot signal broadcast by the base station. The channels on the respective multi-antennas are used to obtain all channel estimates between the respective mobile station antenna and the base station antenna. Based on this channel estimation, the mobile station determines the uplink transmitting antenna according to some criteria. It can be a transmission The antenna may also be multiple transmitting antennas. Using the determined uplink transmitting antennas, the mobile station transmits data upstream during the uplink transmission time period from the next uplink transmission time. One or more of these are selected as described herein. The root antenna is the antenna that selects the maximum received signal strength or the sum of the signal-to-noise ratio. At the same time, the mobile station also connects according to its own difference. All received pilot signals on the receiving antenna, one or more antennas of the base station are selected as transmitting antennas, and the base station is notified to use the antenna selected by the mobile station to transmit signals to the mobile station during the next downlink transmission. The selected one or more antennas is the antenna that selects the maximum received signal strength or the sum of the signal-to-noise ratio of the transmitted signals on all mobile station antennas. After receiving the notification from the mobile station, the base station starts from the next downlink. At the time of transmission, the antenna selected by the mobile station is selected to transmit data for the mobile station during the downlink transmission time period, and the public pilot signal is continuously broadcast in a fixed allocated time slice to provide the mobile station for channel estimation at the next time.

The method described in the present invention does not exclude the use of a base station smart antenna. In the base station's downlink transmission, if multiple antennas are completely or strongly correlated, these multiple antennas can also be used. The antenna achieves directional transmission. In directional transmission, the signals transmitted by multiple antennas are exactly the same, and the channels they experience are also basically the same. The difference is only that the weighting value is different, which results in spatial directional transmission. Therefore, the effect is still equivalent to a single antenna transmission.

FIG. 1 is an example diagram of a multi-antenna time division duplex system to which the present invention is applied. According to the figure, the base station has 4 antennas, and the mobile station has 6 antennas. Figure 3 is a schematic diagram of uplink and downlink transmission period allocation. Referring to FIG. 3, if a time division duplex method is adopted, an uplink transmission period and a downlink transmission period can be divided into one transmission period. The base station transmits a common pilot within a certain fixed time of the downlink transmission period. During this time period, the base station does not transmit other data signals, and different transmitting antennas can use code division to transmit pilots with different code spreading, which is convenient for mobile stations to measure different channels.

According to the setting of Fig. 1, the 4 antennas of the base station transmit pilot signals of different codes within the common pilot time slice of the downlink transmission period. The six receiving antennas of the mobile station estimate different channels based on these pilot signals. There are 24 channels in total, which are expressed in the form of a matrix:

"

Among them, ½ represents the channel that the transmitted signal of the / th base station antenna reaches the z'th mobile station antenna. Due to the use of the time division duplex method, during the uplink transmission period in the next transmission period, the channel that the transmission signal of the first mobile station antenna reaches when it reaches the base station antenna is also roughly ½. Based on this phenomenon, the mobile station's uplink in the next transmission cycle During the transmission period, the antenna used for uplink transmission can be selected according to the channel estimation result in formula (6). Depending on the channel conditions and the amount of data to be transmitted, a transmit antenna or multiple transmit antennas are selected. Assuming that the mobile station needs to select two transmitting antennas, the principle for the mobile station to select antennas can be the principle that the sum of the energy received by all transmitting antenna signals on the antenna is the largest. In the channel expressed by formula (6), the matrix The sum of the squared amplitudes of the elements of a row, ∑ ″ ½ | ² , 1≤ ^ ≤6, select the antenna corresponding to this flat ^ and the largest i as the transmitting antenna. Assuming that the mobile station selects the first and third antennas to transmit signals to the base station, that is, in the above formula for calculating the sum of squares, z '= 1, ³ , the mobile station can send data to the two antennas for transmission. In addition, the mobile station also selects the transmitting antenna that the base station should use for the next transmission according to the channel in formula (6). The selection principle may be the principle that the sum of the received signal energy of the transmitting antenna on all receiving antennas of the mobile station is the largest. That is, the mobile station calculates the sum of the squared amplitudes of the elements of each column in the matrix of formula (6), ι · Ι | ² , 1≤7'≤4, assuming that the formula gets the maximum value when / = 1, that is, lAnl ² + l½ | ² + l½ | ² + lA ₄ il ² + | A ₅ il ² + l /? 6il ^{2 is the} maximum, then the mobile station can notify the base station to use antenna 1 for transmission during the downlink transmission period. The base station receives signals using 4 antennas at the same time, and obtains from the mobile station which antenna or antennas should be used for the mobile station to transmit signals during the downlink transmission period of the transmission period. Through the cyclic execution of the above process, high-speed data communication between the base station and the mobile station is finally achieved. In the above communication process, assuming that the mobile station has learned that there is a strong correlation between the first antenna and the second antenna of the base station, and the directional transmission of the smart antenna can be achieved. When the base station learns from the mobile station, it needs to Signaling using one of these two antennas When transmitting, you can also select two antennas to transmit the same signal at the same time, and achieve different directional transmission by different weighting.

The invention also provides the following signal transmission and reception method based on the time division duplex mode. When a mobile station receives broadcast information from a base station, it can detect the strength of the signals received by multiple receiving antennas. In the uplink transmission, the antenna with the strongest signal detected at the previous moment is used as the transmitting antenna, and during the uplink transmission period The internal transmission uplink signal may be a pilot signal transmitted by the base station, a broadcast signal transmitted by the base station, or a dedicated channel signal transmitted by the base station to the mobile station. After receiving the transmission signal from the user, the base station may use the antenna with the strongest received signal as the downlink transmission antenna to transmit downlink data to the user during the downlink transmission period. Regardless of whether it is at the base station side or the mobile station side, the selected transmitting antenna is the antenna with the highest received signal strength or the highest signal-to-noise ratio (signal-to-interference ratio). Of course, the selection of a single transmitting antenna can also be selected according to other principles.

The method described in the present invention does not exclude the use of a base station smart antenna. In the downlink transmission of the base station, if multiple antennas are completely correlated or strongly correlated, the multiple antennas may also be used for directional transmission. In directional transmission, the signals transmitted by multiple antennas are completely the same, and the channels they experience are also basically the same. The difference is only the difference in the weighting value, which results in spatial directional transmission. Therefore, the effect is still equivalent to a single antenna transmission.

Claims

Rights request

1. A method for selecting a transmitting antenna in a multi-antenna communication environment, comprising:

The signal receiving end selects one or more antennas from the multiple antennas of the signal transmitting end as transmitting antennas according to the measured signal-to-noise ratio of the receiving channel. If one is selected, the signal transmitting end is notified to the signal transmitting end, otherwise, the signal receiving end is based on The channel space vectors obtained on all receiving antennas are used to calculate the correlation between the space vectors. Based on the correlation, one or more of the multiple antennas at the signal transmitting end are selected as the transmitting antennas, and the selection result is notified to the signal transmitting end. ;

2. The method for selecting a transmitting antenna in a multi-antenna communication environment according to claim 1, wherein the correlation between the calculated space vectors is based on the following formula:

ay = \ h * hj \ l .j (h * hi) (hj h ^). '

Where is the correlation coefficient between the channel space column vector of the first transmitting antenna and the channel space column vector of the / th transmitting antenna, which represents the conjugate transpose of the complex number vector, and the conjugate transpose of the complex number vector, then Represents the modulus of taking a complex number.

3. According to the method for selecting a transmitting antenna in a multi-antenna communication environment according to claim 2, it is characterized by: according to the minimum correlation of the channel space vector and the channel space vector Select the transmitting antenna for the principle of the square sum of the modes of the elements.

4. The method for selecting a transmitting antenna in a multi-antenna communication environment according to claim 1, 2 or 3, wherein the method further comprises: when the method is implemented based on a time division duplex system, the signal transmitting end is The base station, the signal receiving end is a mobile station, and the mobile station simultaneously determines the uplink and downlink multi-antenna channel conditions according to the pilot of the base station to directly select the uplink transmitting antenna.

5. The method for selecting a transmitting antenna in a multi-antenna communication environment according to claim 1, wherein the multiple antennas of the signal transmitting end and the signal receiving end are set according to the principle that the noise received by each antenna is independent of each other.

6. The method for selecting transmitting antennas in a multi-antenna communication environment according to claim 4, characterized in that: multiple antennas of a signal transmitting end and a signal receiving end are based on the principle that channels of different transmitting antennas reach different receiving antennas are independent of each other. Settings.

7. The method for selecting a transmitting antenna in a multi-antenna communication environment according to claim 5, characterized in that: the plurality of antennas are set according to the principle that the noise received by each antenna is independent of each other, and for the base station side, between adjacent antennas The distance is greater than or equal to "^; For the mobile station side, the distance between adjacent antennas is greater than or equal to; where α is the serving sector angle of the base station, and A is the carrier wavelength.

8. The method for selecting a transmitting antenna in a multi-antenna communication environment according to claim 5, characterized in that: the plurality of antennas are set according to the principle that the noise received by each antenna is independent of each other, and the phase relationship between the base station side and the mobile station side is The distance between adjacent antennas is greater than or equal to; where is the carrier wavelength.

9. Signaling based on time division duplex mode using the method of claim 5 The transmitting and receiving method is characterized by including:

Step 1: All antennas of the base station transmit pilot signals within a fixed allocated time period; Step 2: The mobile station measures all received pilot signals on its different receiving antennas, and selects one or more antennas, As an uplink transmitting antenna, since the next uplink transmitting moment, a selected antenna is used as a transmitting antenna, and a signal is transmitted within an uplink transmitting time period;

Step 3: The mobile station selects one or more antennas of the base station as transmitting antennas according to all received pilot signals on its different receiving antennas, and notifies the base station to use the antennas selected by the mobile station in the next downlink transmission Transmit signals to the mobile station; Step 4: The base station uses multiple antennas to receive signals from the mobile station, and according to the mobile station's notification, selects one or more antennas as downlink transmitting antennas, and from the next downlink transmission time, A signal is transmitted to the mobile station during the downlink transmission period.

10. The method for transmitting and receiving signals based on time division duplexing according to claim 9, characterized in that: in step 1, all antennas of the base station transmit pilot signals in a code division manner within a fixed allocated time period.

11. The method for transmitting and receiving signals based on time division duplexing according to claim 10, characterized in that: the transmitting pilot signals in the code division mode is that all antennas of the base station select the same one within a fixed allocated time period The codes are transmitted as pilots through codes obtained by different cyclic shifts.

12. The method for transmitting and receiving signals based on time division duplexing according to claim 9, characterized in that: in step 1, all antennas of the base station transmit pilot signals in a time division manner within a fixed allocated time period.

13. The method for transmitting and receiving signals based on time division duplexing according to claim 9, 10, 11 or 12, characterized in that: one or more of the antennas selected in step 1 is received. All antennas with the largest transmitted signal strength or the sum of the signal-to-noise ratio.

14. The method for transmitting and receiving signals based on time division duplexing according to claim 13, characterized in that: the one or more antennas selected in step 3 are transmitting signals on all mobile station antennas Antenna with the largest received signal strength or S / N ratio.

15. The method for transmitting and receiving signals based on time division duplexing according to claim 14, characterized in that: in step 4, when the channels of multiple antenna signals on the base station side are strongly correlated, multiple base station side channels are selected simultaneously. The antennas transmit the same signal, and different antennas are weighted differently to achieve directional transmission of downlink signals.

16. A method for transmitting and receiving signals based on a time division duplex mode using the method according to claim 5, comprising:

Step 11: The mobile station measures received signals on different receiving antennas on the local side, selects one of the antennas as an uplink transmitting antenna, and at the next uplink transmitting moment, uses the selected antenna as a transmitting antenna during the uplink transmitting period. Internal emission signal

Step 12: The base station selects one of the antennas as a downlink transmitting antenna according to the signals of the mobile station received on the multiple antennas on the local side, and transmits a signal to the mobile station in the downlink transmitting time period at the next downlink transmission time.

17. The method for transmitting and receiving signals based on time division duplexing according to claim 16, wherein: the received signals on different antennas measured by the mobile station in step 11 are pilot signals transmitted by a base station.

18. The method for transmitting and receiving signals based on time division duplexing according to claim 16, characterized in that: the received signals on different antennas measured by the mobile station in step 11 are broadcast signals transmitted by a base station.

19. The method for transmitting and receiving signals based on time division duplexing according to claim 16, characterized in that: the received signals on different antennas measured by the mobile station in step 11 are dedicated channels transmitted by the base station to the mobile station. signal.

20. The method for transmitting and receiving signals based on time division duplexing according to claim 16, 17, 18 or 19, characterized in that: one of the antennas selected in step 11 and step 12 is selected reception The antenna with the highest signal strength or signal-to-noise ratio.

21. The method for transmitting and receiving signals based on time division duplexing according to claim 20, characterized in that: when the base station transmits a signal in step 12, when the channels of multiple antenna signals on the base station side are strongly correlated, the base station is selected at the same time Multiple antennas on the side transmit the same signal, and directional transmission of the signal is achieved by weighting different antennas differently.