CN102739282B - Multi-antenna combined detection system of TD-SCDMA system and multi-antenna combined detection method thereof - Google Patents
Multi-antenna combined detection system of TD-SCDMA system and multi-antenna combined detection method thereof Download PDFInfo
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Abstract
The invention relates to a multi-antenna combined detection system of a TD-SCDMA system and a multi-antenna combined detection method thereof. The detection system comprises a plurality of antennas, a plurality of data separation units, a plurality of channel estimation units, a channel estimation postprocessing unit and a combined detection unit. All the antennas are used for receiving signals. The data separation units, which are respectively connected with the antennas, are used for separating training sequences and to-be-demodulated data in the received signals of the corresponding antennas. All the channel estimation units that are respectively connected with the data separation units are used for carrying out channel estimation by utilizing the training sequences. The channel estimation postprocessing unit utilizes channel estimation results of the plurality of channel estimation units to generate a channel system matrix. And the combined detection unit utilizes the channel system matrix and the to-be-demodulated data to calculate estimation values of useful signals in the received signals.
Description
Technical Field
The invention relates to a TD-SCDMA system, in particular to a multi-antenna joint detection system of the TD-SCDMA system.
Background
With the development of wireless communication technology and the worldwide rise of 3G, wireless resources are not becoming more and more strained as a limited resource. For TD-SCDMA systems, which is one of the mainstream standards of 3G, their allocated radio resources are also very limited. In order to improve the frequency spectrum utilization rate of the TD-SCDMA system, the same-frequency networking becomes an effective solution. However, co-frequency networking also brings co-frequency interference while improving spectrum efficiency. The co-channel interference refers to interference between users in different cells caused by data transmission in neighboring cells using the same carrier frequency and the same spreading factor. The performance of the system in various aspects such as the capacity and the communication quality is reduced due to the co-channel interference.
Co-channel interference is one of Multiple Access Interference (MAI). TD-SCDMA systems employ joint detection algorithms to overcome Multiple Access Interference (MAI). Meanwhile, for the interference of the adjacent cell, the stronger adjacent cell interference can be brought into the joint detection by estimating the channel impulse response of the adjacent cell, so that the stronger adjacent cell interference is eliminated.
However, due to the consideration of implementation complexity and other factors, the current joint detection algorithm currently adopts single-antenna processing, and the maximum number of supported code channels is 16. When the number of interference sources in the neighboring cell is large, the total number of code channels is larger than 16. At this time, a part of code channels cannot participate in joint detection, so that the part of multiple access interference cannot be eliminated.
Disclosure of Invention
The invention aims to provide a multi-antenna joint detection system and a method of a TD-SCDMA system, which can still eliminate co-frequency multiple access interference under the condition of increasing the number of code channels.
The invention provides a multi-antenna joint detection system of a TD-SCDMA system, which comprises a plurality of antennas, a plurality of data separation units, a plurality of channel estimation units, a channel estimation post-processing unit and a joint detection unit. Each antenna is used to receive a signal. Each data separation unit is connected with an antenna respectively and used for separating the training sequence and the data to be demodulated in the received signals of the corresponding antenna. Each channel estimation unit is connected with a data separation unit respectively and used for carrying out channel estimation by utilizing the training sequence. The channel estimation post-processing unit generates a channel system matrix by using the channel estimation results of the plurality of channel estimation units. The joint detection unit calculates the estimation value of the useful signal in the received signal by using the channel system matrix and the data to be demodulated.
In one embodiment of the present invention, each antenna supports a predetermined number of code channels.
In an embodiment of the present invention, the joint detection unit limits the number of code channels participating in joint detection, so that the number of code channels is less than or equal to the rank of the channel system matrix.
In an embodiment of the present invention, the joint detection unit limits the number of code channels participating in joint detection by raising a threshold for code channel activation detection.
In an embodiment of the present invention, the number of the antennas, the data separation unit and the channel estimation unit is two.
In one embodiment of the present invention, the estimate of the desired signal is a minimum mean square error estimate.
The invention also provides a multi-antenna joint detection method of the TD-SCDMA system, which comprises the following steps: receiving signals by a plurality of antennas, wherein the received signals comprise training sequences and data to be demodulated; carrying out data separation on the received signals of each antenna to respectively obtain a training sequence and data to be demodulated; performing channel estimation on each antenna by using the training sequence; merging the channel estimation results of a plurality of antennas for post-processing to obtain a channel system matrix; and calculating an estimated value of a useful signal in the received signal by using the channel system matrix and the data to be demodulated.
In one embodiment of the present invention, each antenna supports a predetermined number of code channels.
In an embodiment of the present invention, the method further includes limiting the number of code channels participating in the joint detection so that the number of code channels is less than or equal to the rank of the channel system matrix.
In an embodiment of the present invention, the number of code channels participating in joint detection is limited by raising the threshold for code channel activation detection.
In an embodiment of the present invention, the number of the antennas is two.
In one embodiment of the present invention, the estimate of the desired signal is a minimum mean square error estimate.
Compared with the joint detection system in the prior art, the multi-antenna joint detection system provided by the invention can improve the receiving performance through diversity reception and improve the same frequency resistance through spatial multiplexing, thereby more accurately separating useful signals from the received signals and further obviously improving the demodulation performance of the received signals.
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In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below, wherein:
fig. 1 illustrates a dual antenna receive baseband model according to an embodiment of the present invention.
FIG. 2 illustrates a joint detection system according to an embodiment of the present invention.
Fig. 3 illustrates a joint detection method according to an embodiment of the present invention.
Detailed Description
The following description will be made in detail by taking a TD-SCDMA wireless communication system as an example, so as to provide a thorough understanding of the multi-antenna joint detection system of the present invention. For simplicity of description, two antennas will be exemplified in the following description. For the case where the system contains more than two antennas, the model is similar to that described below.
FIG. 1 illustrates a system baseband model according to an embodiment of the present invention, wherein e1And e2Respectively for the received data to be demodulated for both antennas. A. the(1)And A(2)Channel system matrix on two antennas respectively, wherein in sub-blockAnd representing the channel vector of the ith code channel on the jth antenna.Indicating the jth symbol on the ith code track. n is1And n2Respectively representing white Gaussian noise, n, contained in the received signaliIs a variance of σ2And obey a normal distribution N (0, σ)2) White gaussian noise.
In TD-SCDMA wireless communication system, the data to be demodulated in the received signal can be generally defined as:
e＝A·d+n (1.1)
where a is the channel system matrix, d is the desired signal, and n is white gaussian noise contained in the received signal.
As known from the baseband model, the channel system matrix for dual antenna reception extends to:
the data to be demodulated is expanded into:
the gaussian white noise spread contained in the received signal is:
as a result of the two-antenna joint detection, similar to the principle of single-antenna joint detection, the Minimum Mean Square Error (MMSE) estimate of the useful signal d is:
wherein,minimum mean square error estimate, A, representing the useful signal dHDenotes the conjugate transpose of the channel system matrix a and I denotes the identity matrix.
The system for multi-antenna joint detection described in the present invention integrates multi-antenna diversity reception and spatial multiplexing. The method can improve the receiving performance through diversity reception, and can also improve the same frequency resistance through spatial multiplexing, thereby more accurately separating useful signals from the received signals and further obviously improving the demodulation performance of the received signals. Specifically, when the total number of the code channels detected in a combined mode is lower than 16 code channels, the system is equivalent to a multi-antenna diversity receiving system, and good diversity gain is obtained; when the total code channel number of the joint detection is 32 code channels, the system is equivalent to a spatial multiplexing system and supports that the 32 code channels simultaneously participate in the joint detection; and when the number of code channels is between 16 and 32, the diversity gain and the multiplexing gain (the same frequency resistance capability) are provided.
Based on the above analysis, a joint detection system according to one embodiment of the present invention is described as shown in FIG. 2. As shown in fig. 2, the joint detection system 200 includes: two antennas 201, 202, two data separation units 211, 212, two channel estimation units 221, 222, a channel estimation post-processing unit 230 and a joint detection unit 240. Each data separation unit and each channel estimation unit correspond to one antenna. For example, the first data separation unit 211 and the first channel estimation unit 221 correspond to the first antenna 202; the second data separation unit 212 and the second channel estimation unit 222 correspond to the second antenna 202.
Specifically, the two data separation units 211 and 212 are used to separate the training sequences and the data to be demodulated in the signals received from the two antennas 201 and 202, respectively.
Two channel estimation units 221 and 222 perform channel estimation using the training sequence.
The channel estimation post-processing unit 230 generates a channel system matrix a using the channel estimation results of the two channel estimation units 221 and 222. Here, the channel system matrix a is a two-antenna channel system matrix a as shown in fig. 1(1)And A(2)And (3) combining the components.
The joint detection unit 240 calculates a minimum mean square error estimate of the desired signal in the received signal using the channel system matrix and the data to be demodulatedFor subsequent demodulation and decoding.
Correspondingly, fig. 3 illustrates a joint detection method according to an embodiment of the present invention. Referring to fig. 3, in step S300, signals are received by a plurality of antennas, and then in step S301, data separation is performed on the received signals of each antenna to separate the training sequence and the data to be demodulated therein. In step S302, a channel estimation is performed for each antenna using a training sequence. Then, in step S303, the channel estimation results of the multiple antennas are merged and post-processed to obtain a channel system matrix a. Finally, in step S304, the channel is utilizedSystem matrix and data to be demodulated, calculating minimum mean square error estimate of useful signal
It is noted that although the above has been given for an embodiment in which the joint detection employs minimum mean square error estimation, it should be appreciated that the communication system and the user equipment of the present invention are not limited to this example, but may employ other methods of estimation.
In addition, in the engineering implementation, it cannot be guaranteed that data received by the two antennas are completely independent. The correlation of data between antennas means that the channel system matrix a is not of full rank, where the decomposition of the correlation matrix is unstable, thereby deteriorating the demodulation performance for the received signal. Therefore, it is necessary to avoid this situation by adding some protection measures, such as the joint detection unit 240 ensuring the stability of matrix decomposition by limiting the number of code channels participating in joint detection so that the number of code channels is less than or equal to the rank of the matrix. In an embodiment, the joint detection unit 240 may prevent a situation of a large number of code channels caused by false detection of code channel activation by increasing a threshold of code channel activation detection.
Compared with the traditional single-antenna common-frequency joint detection system, the channel estimation post-processing unit of the multi-antenna joint detection system described in the embodiment of the invention simultaneously outputs the channel system matrixes of two antennas, so that the joint detection unit can combine the channel system matrixes of the two antennas to carry out MIMO detection; and because MIMO detection is adopted, the joint detection can detect data with more code channels. Taking two antennas as an example, data of 32 code channels can be detected at most.
Therefore, compared with the traditional single-antenna co-frequency joint detection system, the multi-antenna joint detection system provided by the embodiment of the invention has stronger joint detection capability, improves the co-frequency interference resistance capability, and has certain diversity gain under the condition that a channel system matrix is not of a full rank. In addition, the multi-antenna joint detection system can be regarded as a system combining MIMO and joint detection, and can be smoothly evolved to a MIMO-CDMA system.
Although the present invention has been described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (12)
1. A multi-antenna joint detection system of TD-SCDMA system, comprising:
the receiving signals of each antenna comprise the same-frequency interference signals of adjacent regions;
each data separation unit is connected with one antenna and used for separating the training sequence in the received signal of the corresponding antenna from the data to be demodulated;
a plurality of channel estimation units, each of which is connected with a data separation unit respectively and used for carrying out channel estimation by utilizing the training sequence;
the channel estimation post-processing unit generates a channel system matrix by using the channel estimation results of the plurality of channel estimation units, wherein the channel system matrix comprises M code channels, M is more than 16, and at least (M-16) adjacent region code channels;
and the joint detection unit calculates the estimation value of the useful signal in the received signal by utilizing the channel system matrix and the data to be demodulated.
2. The system of claim 1, wherein each antenna supports a predetermined number of code channels.
3. The system of claim 1 wherein the joint detection unit limits the number of code channels involved in joint detection such that the number of code channels is less than or equal to the rank of the channel system matrix.
4. The system of claim 3, wherein the joint detection unit limits the number of code channels participating in joint detection by raising a threshold for code channel activation detection.
5. The system of claim 1, wherein the number of antennas, data separation units, and channel estimation units are all two.
6. The system of claim 1 wherein the estimate of the desired signal is a minimum mean square error estimate.
7. A multi-antenna joint detection method of TD-SCDMA system includes the following steps:
utilizing a plurality of antennas to receive signals, wherein the received signals comprise training sequences and data to be demodulated, and the received signals of each antenna comprise co-channel interference signals of adjacent regions;
carrying out data separation on the received signals of each antenna to respectively obtain a training sequence and data to be demodulated;
performing channel estimation on each antenna by using the training sequence;
combining the channel estimation results of a plurality of antennas and carrying out post-processing to obtain a channel system matrix, wherein the channel system matrix comprises M code channels, M is more than 16, and at least (M-16) adjacent code channels; and
and calculating an estimated value of the useful signal in the received signal by using the channel system matrix and the data to be demodulated.
8. The method of claim 7, wherein each antenna supports a predetermined number of code channels.
9. The method of claim 7, further comprising limiting a number of code channels participating in joint detection such that the number of code channels is less than or equal to a rank of the channel system matrix.
10. The method of claim 9, wherein the number of code channels participating in the joint detection is limited by raising a threshold for code channel activation detection.
11. The method of claim 7, wherein the number of antennas is two.
12. The method of claim 7 wherein the estimate of the desired signal is a least mean square error estimate.
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| CN1604512A (en) * | 2003-09-29 | 2005-04-06 | 富士通株式会社 | United detecting method and apparatus |
| CN1770650A (en) * | 2004-10-15 | 2006-05-10 | 展讯通信（上海）有限公司 | Maximum ratio combining of channel estimation for joint detection in TD-SCDMA systems |
| CN101257324A (en) * | 2007-02-28 | 2008-09-03 | 展讯通信（上海）有限公司 | Linear combined channel estimation method in TD-SCDMA system |
| CN101267585A (en) * | 2007-03-16 | 2008-09-17 | 展讯通信（上海）有限公司 | Method and receiving device for TD-SCDMA system to send and receiving broadcast service |
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| CN1604512A (en) * | 2003-09-29 | 2005-04-06 | 富士通株式会社 | United detecting method and apparatus |
| CN1770650A (en) * | 2004-10-15 | 2006-05-10 | 展讯通信（上海）有限公司 | Maximum ratio combining of channel estimation for joint detection in TD-SCDMA systems |
| CN101257324A (en) * | 2007-02-28 | 2008-09-03 | 展讯通信（上海）有限公司 | Linear combined channel estimation method in TD-SCDMA system |
| CN101267585A (en) * | 2007-03-16 | 2008-09-17 | 展讯通信（上海）有限公司 | Method and receiving device for TD-SCDMA system to send and receiving broadcast service |
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