CN107547119B - Transmission mode self-adaption method and device based on correlation between channels - Google Patents
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Abstract
The embodiment of the invention provides a transmission mode self-adaption method and a device based on correlation between channels, wherein the method comprises the following steps: performing channel estimation on a current frame of a receiving end to obtain a channel matrix; performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein diagonal elements in the diagonal matrix are singular values of the channel matrix; calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the condition number of the current frame; judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, wherein the channel type comprises a line-of-sight (LOS) channel or a non-NLOS channel. By applying the embodiment of the invention, the throughput performance of the link can be improved.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a transmission mode adaptive method and apparatus based on inter-channel correlation.
Background
In an indoor broadband mobile communication system, a communication link between a base station and a mobile station is established by alternating between LOS (Line of Sight) in which a transmitting and receiving antenna must be directly visible at two points without being blocked in the middle and NLOS (Non-Line of Sight) in which the Line of Sight of two points requiring communication is blocked and the other cannot be seen at each other in wireless communication. In order to meet the increasing demand for high-rate data transmission, data transmission of LOS communication link and NLOS communication link can be realized by configuring Multiple antennas between the base station and the mobile station, thereby constituting a MIMO (Multiple Input Multiple Output) system, in which spatial diversity and spatial multiplexing are the main usage technologies of the MIMO system.
The existing transmission mode based on the correlation between channels adopts a spatial multiplexing transmission mode for simultaneously comprising an LOS communication link and an NLOS communication link between a base station and a mobile station. Specifically, a plurality of antennas are firstly used at a receiving end and a transmitting end, so that multipath components can be generated in the spatial propagation process of the plurality of antennas, then the multipath components in the spatial propagation are fully utilized, and a plurality of data channels (MIMO sub-channels) generated by the multipath components are used for transmitting signals on the same frequency band, so that the channel capacity is linearly increased along with the increase of the number of the antennas. This increase in channel capacity does not require additional bandwidth to be occupied nor additional transmit power to be consumed, and is therefore a very effective means of increasing channel and system capacity.
However, for an indoor scenario, especially in the case of sparse distribution of small base stations, the communication link between the base station and the mobile station will face more frequent alternation between LOS and NLOS, for the link NLOS, the spatial multiplexing may bring higher throughput performance, but for LOS with link quality better than NLOS, the spatial multiplexing transmission mode may cause the throughput performance of the link to be degraded.
Disclosure of Invention
The embodiment of the invention aims to provide a transmission mode self-adaption method and device based on correlation between channels so as to improve the throughput performance of a link. The specific technical scheme is as follows:
the embodiment of the invention discloses a transmission mode self-adaption method based on correlation between channels, which comprises the following steps:
performing channel estimation on a current frame of a receiving end to obtain a channel matrix;
performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein diagonal elements in the diagonal matrix are singular values of the channel matrix;
calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the condition number of the current frame, wherein the condition number represents the correlation size between channels;
judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, wherein the channel type comprises a line-of-sight (LOS) channel or a non-NLOS channel.
Optionally, the performing singular value decomposition on the channel matrix to obtain a diagonal matrix, where diagonal elements in the diagonal matrix represent singular values of the channel matrix, includes:
according to the formula
Performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein m × m, m × n and n × n respectively represent the rank of the matrix, m represents the number of transmitting-end antennas, n represents the number of receiving-end antennas, H represents the channel matrix, U represents a left unitary matrix, U1, …, Um, … and U represent unitary matrices, and the channel matrix is divided into m × m, m × n and n × nm(m-1)+1，…，Um×mRespectively, elements of the left unitary matrix, S denotes a diagonal matrix, S1, …, Sm × n respectively, elements of the diagonal matrix, denote singular values of the channel matrix, H denotes a right unitary matrix, V1, …, Vn, …, Vn(n-1)+1，…，Vn×nRespectively, elements of the left unitary matrix.
Optionally, the determining whether the condition number is greater than a preset condition number threshold to obtain a determination result, determining a channel type of the current frame corresponding to the determination result, and determining a transmission mode of the current frame according to the channel type includes:
judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result;
if the judgment result is that the condition number is larger than the preset condition number threshold value, determining that the channel type of the current frame corresponding to the judgment result is the LOS channel, and adopting a space diversity transmission mode for the LOS channel;
and if the judgment result is that the condition number is smaller than or equal to the preset condition number threshold value, determining that the channel type of the current frame corresponding to the judgment result is the NLOS channel, and adopting a spatial multiplexing transmission mode for the NLOS channel.
Optionally, after determining the channel type of the current frame corresponding to the determination result and determining the transmission mode of the current frame according to the channel type, the method further includes:
and taking the transmission mode of the current frame as the transmission mode corresponding to the frame in the adjacent preset period after the current frame.
The embodiment of the invention discloses a transmission mode self-adaptive device based on correlation between channels, which comprises:
the estimation module is used for carrying out channel estimation on the current frame of the receiving end to obtain a channel matrix;
the decomposition module is used for carrying out singular value decomposition on the channel matrix to obtain a diagonal matrix, and diagonal elements in the diagonal matrix are singular values of the channel matrix;
the calculation module is used for calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, taking the ratio as the condition number of the current frame, and the condition number represents the size of the correlation between channels;
and the judging module is used for judging whether the condition number is greater than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, wherein the channel type comprises a line-of-sight (LOS) channel or a non-line-of-sight (NLOS) channel.
Optionally, the decomposition module is specifically configured to:
according to the formula
Performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein m × m, m × n and n × n respectively represent the rank of the matrix, m represents the number of transmitting-end antennas, n represents the number of receiving-end antennas, H represents the channel matrix, U represents a left unitary matrix, U1, …, Um, … and U represent unitary matrices, and the channel matrix is divided into m × m, m × n and n × nm(m-1)+1，…，Um×mAre respectively asElements of the left unitary matrix, S denotes a diagonal matrix, S1, …, and Sm × n are elements of the diagonal matrix, respectively, denote singular values of the channel matrix, H denotes a right unitary matrix, V1, …, Vn, …, Vn(n-1)+1，…，Vn×nRespectively, elements of the left unitary matrix.
The judging module comprises:
the judgment submodule is used for judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result;
a first determining submodule, configured to determine that the channel type of the current frame corresponding to the determination result is the LOS channel and apply a space diversity transmission mode to the LOS channel if the determination result indicates that the condition number is greater than the preset condition number threshold value;
and a second determining submodule, configured to determine that the channel type of the current frame corresponding to the determination result is the NLOS channel and adopt a spatial multiplexing transmission mode for the NLOS channel, if the determination result indicates that the condition number is smaller than or equal to the preset condition number threshold value.
The device further comprises:
and the determining module is used for taking the transmission mode of the current frame as the transmission mode corresponding to the frame in the adjacent preset period after the current frame.
The embodiment of the invention also discloses electronic equipment which comprises a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory finish mutual communication through the communication bus;
the memory is used for storing a computer program;
the processor is configured to implement the above-mentioned transmission mode adaptive method based on inter-channel correlation when executing the program stored in the memory.
In yet another aspect of the present invention, a computer-readable storage medium is further disclosed, wherein instructions are stored in the computer-readable storage medium, and when the instructions are executed on a computer, the computer is caused to execute any one of the transmission mode adaptation methods based on inter-channel correlation.
The embodiment of the invention provides a transmission mode self-adaptive method and a device based on correlation between channels, which comprises the steps of firstly carrying out channel estimation on a current frame of a receiving end to obtain a channel matrix; then, singular value decomposition is carried out on the channel matrix to obtain a diagonal matrix; then calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the condition number of the current frame; and finally, judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type. The condition number is used as a correlation index between channels, the size of the condition number of the current frame and a preset condition number threshold value is judged, whether the current frame is an LOS channel type or an NLOS channel type is determined according to the judgment result, and finally the transmission mode of the current frame is determined according to the channel type. Therefore, different transmission modes are adopted for different channel types, so that the LOS channel type and the NLOS channel type can both adopt the transmission mode for improving the throughput performance of the link, and the throughput performance of the link is greatly improved. Of course, it is not necessary for any product or method of practicing the invention to achieve all of the above-described advantages at the same time.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flowchart of a transmission mode adaptive method based on inter-channel correlation according to an embodiment of the present invention;
fig. 2 is a topological diagram of a static scene between channels according to an embodiment of the present invention;
fig. 3 is a topology diagram of a dynamic scenario between channels according to an embodiment of the present invention;
FIG. 4 is a graph illustrating a cumulative channel condition number distribution for line-of-sight and non-line-of-sight according to an embodiment of the present invention;
fig. 5 is a schematic flowchart of another transmission mode adaptation method based on inter-channel correlation according to an embodiment of the present invention;
fig. 6 is a diagram of simulation results of a transmission mode based on correlation between channels according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a transmission mode adaptive apparatus based on inter-channel correlation according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In recent years, the indoor broadband mobile communication system focuses on improving the transmission rate and capacity in hot spots and indoor coverage scenes, and compared with other scenes, the indoor scenes have larger bandwidth and lower mobile station moving speed, so that the indoor broadband mobile communication has better indoor channel environment and higher peak throughput, and the transmission rate of the indoor broadband mobile communication system is greatly improved. However, for indoor scenarios, especially in the case of sparse distribution of small base stations, the communication link between the base station and the mobile station will face more frequent alternation between LOS and NLOS, which is a new issue to be considered in indoor scenarios compared to outdoor macro base station scenarios. Based on this, the invention provides a transmission mode self-adapting method based on correlation between channels, which comprises the following specific processes:
referring to fig. 1, fig. 1 is a flowchart illustrating a transmission mode adaptive method based on inter-channel correlation according to an embodiment of the present invention, including the following steps:
s101, channel estimation is carried out on the current frame of the receiving end to obtain a channel matrix.
In particular, the wireless channel has a large randomness, which causes distortion to the amplitude, phase and frequency of the received signal, thereby providing a large challenge to the design of the receiver. Meanwhile, in a wireless communication system, diversity, channel equalization, best-match receiver design, maximum likelihood detection, coherent demodulation, adaptive link technology, and the like all need to be supported by good channel estimation. Therefore, the channel estimator is an important component of the receiver, and the channel estimation is also a very important subject in the wireless communication field.
For each frame in the link, the receiving end can obtain a channel matrix through channel estimation. Channel estimation is a process of estimating model parameters of a certain assumed channel model from received data. If the channel is linear, then the channel estimate is an estimate of the system impulse response. It is emphasized that channel estimation is a mathematical representation of the effect of the channel on the input signal, while "good" channel estimation is an estimation algorithm that minimizes some estimation error. Common channel estimation criteria used in wireless communications are the minimum mean square error criterion (MMSE) and the maximum likelihood criterion (ML).
S102, singular value decomposition is carried out on the channel matrix to obtain a diagonal matrix, and diagonal elements in the diagonal matrix are singular values of the channel matrix.
Specifically, since the concept of the condition number is derived from singular value decomposition (SDV) of the channel, when the condition number is used as an index of the channel state information, it is necessary to perform singular value decomposition on the channel matrix first. And performing singular value decomposition on the channel matrix to obtain a left unitary matrix, a diagonal matrix and a right unitary matrix, wherein the elements on the diagonal in the diagonal matrix are the singular values of the channel matrix.
S103, calculating the ratio of the maximum singular value to the minimum singular value in all singular values, and taking the ratio as the condition number of the current frame, wherein the condition number represents the correlation size between channels.
In particular, according to the formula
And calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the Condition Number (CN) of the current frame. Since the magnitude of the singular values in the diagonal matrix measures the "health" of the "degrees of freedom" supported by the channel, a closer value to 0 indicates that the degree of freedom is closer to the "degraded" edge. For example, in the case of two singular values in the "optimal channel", the two singular values are the same in size, which means that the channel supports both degrees of freedom well without any difference, which is an ideal case; however, in the case of two singular values in a "random channel", one is larger and the other is smaller. In other words, this channel supports more than 1 degree of freedom, and is not as effective as 2. Therefore, the condition number is a very valuable parameter, the condition number is defined as the result of the ratio of the maximum singular value to the minimum singular value in the diagonal matrix S, and the closer the ratio (condition number) is to 1, the more the transmission conditions of each parallel sub-channel (degree of freedom) in the channel are very average; the larger the ratio is, the larger the difference and imbalance of the transmission conditions of the sub-channels are. Here, the condition number characterizes the magnitude of correlation between channels, i.e., the magnitude of the degree of freedom of each parallel subchannel between channels.
S104, judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, wherein the channel type comprises a line-of-sight (LOS) channel or a non-NLOS channel.
And determining a decision threshold T with strong and weak channel correlation, and determining the best transmission mode of the current link by using the threshold. In specific operation, singular value decomposition is carried out on the channel matrixes of LOS and NLOS in an indoor system in practical application, a condition number is calculated, and the distance from a receiving signal close to the middle to a base station in all the receiving signals is selected as a judgment value according to the distribution condition of the receiving signals in an indoor scene. Here, the preset condition number threshold may be set according to actual situations, for example, for the topology of the inter-channel static scenario in fig. 2, T-15 may be selected as the decision threshold. After the condition number threshold value (marked as CNT) is determined, comparing the condition number (marked as CN) of the current frame with the CNT, when the CN is greater than the CNT, the correlation of the channel is strong, and the current frame can be judged to be an LOS channel environment, namely the current frame adopts a space diversity transmission mode, otherwise, the correlation of the channel is weak, and the current frame can be judged to be an NLOS channel environment, namely the current frame adopts a space multiplexing transmission mode. The result of such adaptation can cope with the problem of degraded throughput performance when switching between LOS and NLOS environments in a mobile scenario.
Therefore, the transmission mode self-adaptive method based on the correlation between channels provided by the embodiment of the invention comprises the steps of firstly carrying out channel estimation on a current frame of a receiving end to obtain a channel matrix; then, singular value decomposition is carried out on the channel matrix to obtain a diagonal matrix; then calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the condition number of the current frame; and finally, judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type. The condition number is used as a correlation index between channels, the size of the condition number of the current frame and a preset condition number threshold value is judged, whether the current frame is an LOS channel type or an NLOS channel type is determined according to the judgment result, and finally the transmission mode of the current frame is determined according to the channel type. Therefore, different transmission modes are adopted for different channel types, so that the LOS channel type and the NLOS channel type can both adopt the transmission mode for improving the throughput performance of the link, and the throughput performance of the link is greatly improved.
In the past research on transmission mode adaptation, a common transmission mode adaptation method is based on channel quality, but LOS with link quality better than NLOS has strong correlation between antennas, and is not suitable for a transmission mode using TM3 spatial multiplexing. Therefore, for an indoor scenario where LOS and NLOS are frequently alternated, the transmission mode adaptation process should be designed in combination with specific channel characteristics. The indoor scenario on which the present invention is based is described with reference to fig. 2 and 3.
Fig. 2 is a topology diagram of a static scenario between channels according to an embodiment of the present invention. The topology of the static scene shown in fig. 2 is 6 separate rooms around both sides of the lobby, each room having an area of 6m x 6 m. There are two large rooms in the center of the hall, accounting for 8m x 8 m. The thickness degree of the line in the figure represents the thickness condition of the wall body, the thick line represents the thicker wall body, and the thin line represents the thinner wall body. The base station is deployed in the center of the hall for the transmission (Tx) of the signal, and three test points located in the figure, representing static test points UE, the UE being a receiver (Rx), have linear distances of 3m, 15m, 24m from Tx, respectively. Obviously, the propagation mode of the signal between Tx and Rx at a distance of 3m is LOS, the test point at Rx is called "good point", the propagation modes of 15m and 24m are NLOS, and the thickness of the penetrated wall is different, and the test points at Rx are called "middle point" and "bad point", respectively.
Fig. 3 is a topological diagram of a dynamic scene between channels according to an embodiment of the present invention, in the topological diagram of the dynamic scene shown in fig. 3, there are 6 independent rooms around two sides of a hall, and the area of each room is 6m × 6 m. There are two large rooms in the center of the hall, accounting for 8m x 8 m. The thickness degree of the line in the figure represents the thickness condition of the wall body, the thick line represents the thicker wall body, and the thin line represents the thinner wall body. In FIG. 2, a square at A, B, C, D, E, F, G, H, I represents a detection point in the path, and a straight line between A, B, C, D, E, F, G, H, I represents a movement path, and the path of the user movement is X- > A- > B- > C- > D- > E- > D- > C- > B- > F- > G- > H- > I. The moving path from X to a is used to complete initialization and test work of the channel environment and will not be included in the performance simulation. It can be observed that A- > B- > C and C- > B- > F are LOS transmission, and D- > E- > D and G- > H- > I are NLOS transmission (penetrating one thin wall and two thin walls respectively). C- > D, D- > C and F- > G are the LOS to NLOS transition states. It should be noted that the speed of the UE (static detection point) is 3km/h, the total length of the route is 32m, and therefore the total duration of the route is 38.4 s.
From the topology diagrams of the inter-channel static scenario and the dynamic scenario provided in fig. 2 and 3, it can be seen that LOS and NLOS are frequently alternated in the indoor scenario, and therefore, it is necessary to adapt the transmission mode in combination with specific channel characteristics.
In the embodiment of the invention, the channel singular value is adopted to describe the channel correlation characteristic based on the relation between the MIMO channel capacity and the channel singular value. Here, the relationship between the channel capacity and the channel singular value may be represented by the formula:
where H denotes the channel matrix, C denotes the channel capacity, B denotes the channel bandwidth, N denotes the total number of channels, p denotes the average power of the signal,
representing the singular values of the channel matrix, i representing the ith channel, i being a natural number greater than zero. Here, the channel estimation in the formula is a process of estimating model parameters of a certain channel model to be assumed from received data. In the invention, a channel matrix can be determined by carrying out channel estimation on a current frame of a receiving end; then, singular value decomposition is carried out through a channel matrix, so that channel singular values are obtained; finally, the relevant characteristics of the channels are described through the singular values of the channels, and the adaptive transmission mode is selected for the channels according to the relevant characteristics of the channels, so that the transmission mode between the channels is adaptive, and the throughput performance of the link is improved.
In the embodiment of the present invention, singular value decomposition is performed on the channel matrix to obtain a diagonal matrix, which may specifically be:
according to the formula
Performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein m × m, m × n and n × n respectively represent the rank of the matrix, m represents the number of transmitting-end antennas, n represents the number of receiving-end antennas, H represents the channel matrix, U represents a left unitary matrix, U1, …, Um, … and U represent unitary matrices, and the channel matrix is divided into m × m, m × n and n × nm(m-1)+1，…，Um×mRespectively, elements of the left unitary matrix, S denotes a diagonal matrix, S1, …, Sm × n respectively, elements of the diagonal matrix, denote singular values of the channel matrix, H denotes a right unitary matrix, V1, …, Vn, …, Vn(n-1)+1，…，Vn×nRespectively, elements of the left unitary matrix.
Here, the unitary matrix can be simplified by multiplying with its conjugate transpose, wherein the right unitary matrix is used to preprocess the transmitted signal and convert the transmission process into a diagonal matrix form with parallel sub-channels. Here, by performing singular value decomposition on the channel matrix, the condition number is calculated according to the ratio of the singular values, so that the transmission condition of each parallel sub-channel in the channel can be more accurately judged.
Here, the number of singular values is the rank of the channel matrix, and the number of singular values directly reflects the number of degrees of freedom supported by the channel, for example, when the rank of the channel matrix is 2, by the formula:
performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein H represents the channel matrix, U represents a left unitary matrix, U1, U2, U3 and U4 are elements of the left unitary matrix respectively, S represents the diagonal matrix, S1 and S2 are elements of the diagonal matrix respectively and represent singular values of the channel matrix, V represents a right unitary matrix, and V1, V2, V3 and V4 are elements of the left unitary matrix respectively. Here, when the rank of the channel matrix is 2, the condition number is calculated according to the ratio of singular values by performing singular value decomposition on the channel matrix, so that the transmission condition of each parallel subchannel in the channel can be more accurately judged.
For another example, when the rank of the channel matrix is 3, by the formula:
performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein H represents the channel matrix, U represents a left unitary matrix, U1, U2, U3, U4, U5, U6, U7, U8, and U9 are elements of the left unitary matrix, S represents the diagonal matrix, S1, S2, and S3 are elements of the diagonal matrix, represent singular values of the channel matrix, V represents a right unitary matrix, and V1, V2, V3, V4, V5, V6, V7, V8, and V9 are elements of the left unitary matrix. Here, when the rank of the channel matrix is 3, the condition number CN is calculated according to the ratio of singular values by performing singular value decomposition on the channel matrix, so that the transmission condition of each parallel subchannel in the channel can be more accurately determined.
In addition, when the rank of the channel matrix is n, the channel matrix may be subjected to singular value decomposition by the above-described formula of performing singular value decomposition on the channel matrix.
In the embodiment of the present invention, it is determined whether the condition number is greater than a preset condition number threshold value, a determination result is obtained, a channel type of the current frame corresponding to the determination result is determined, and a transmission mode of the current frame is determined according to the channel type, which may specifically be:
firstly, judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result.
Specifically, a decision threshold T of strong and weak channel correlation is determined, that is, a preset condition number threshold is determined, and then the threshold is used to determine the best transmission mode of the current link. During specific operation, singular value decomposition should be performed on the channel matrixes of LOS and NLOS in an indoor system in practical application, condition numbers are calculated according to the maximum singular value and the minimum singular value in the decomposed singular values, and preset condition number threshold values are selected according to distribution conditions. For example, for the profile of fig. 2, T-15 may be selected as the decision threshold.
And secondly, if the condition number is larger than the preset condition number threshold value according to the judgment result, determining that the channel type of the current frame corresponding to the judgment result is an LOS channel, and adopting a space diversity transmission mode for the LOS channel.
After the condition number threshold value (CNT) is determined, comparing the condition number (marked as CN) of the current frame with the CNT, when the CN is greater than the CNT, the correlation of the channel is strong, and the current frame can be judged to be an LOS channel environment, and then the current frame should adopt a space diversity transmission mode. Wherein spatial diversity is achieved using multiple receive antennas. One antenna is used for transmitting at the transmitting end, and a plurality of antennas are used for receiving at the receiving end. The distance d λ/2(λ is the operating wavelength) between the receiving end antennas to ensure that the fading characteristics of the output signals of the receiving antennas are independent from each other, that is, when the output signal of a certain receiving antenna is very low, the output of other receiving antennas does not necessarily have the phenomenon of low amplitude at the same time, and a path with large signal amplitude and optimal signal-to-noise ratio is selected from the output signals of the receiving antennas through corresponding combining circuits to obtain a total output signal of the receiving antennas. This reduces the effects of channel fading and improves the reliability of the transmission. The technique has application in analog frequency division mobile communication systems (FDMA), digital time division systems (TDMA), and code division systems (CDMA). Here, space diversity is adopted for the LOS channel environment, and transmission signal quality is improved.
And thirdly, if the condition number is smaller than or equal to the preset condition number threshold value according to the judgment result, determining that the channel type of the current frame corresponding to the judgment result is an NLOS channel, and adopting a spatial multiplexing transmission mode for the NLOS channel.
Specifically, when CN is less than or equal to CNT, it indicates that the correlation of the channel is weak, and it can be determined as an NLOS channel environment, and the current frame should adopt a spatial multiplexing transmission mode. The result of such adaptation can cope with the problem of degraded throughput performance when switching between LOS and NLOS environments in a mobile scenario. The spatial multiplexing is to use multiple antennas at the transmitting end and the receiving end simultaneously, which can improve the transmission rate of the system by times.
In general, spatial diversity (TM2) and spatial multiplexing (TM3) techniques are the main use techniques for microcells in indoor scenarios. For indoor broadband mobile communication systems, experiments show that using TM3 in LOS results in poor link throughput performance, while using TM3 in NLOS results in higher throughput performance gain than using TM 2. By combining the characteristics of precoding matrixes of different transmission modes, the poor spatial multiplexing effect adopted under LOS is caused by the strong correlation of an LOS channel, and when the correlation index between channels is selected as a judgment factor for judging which transmission mode is adopted under LOS and NLOS, the optimal throughput performance of a link can be obtained.
In order to verify the reasonability of selecting the condition number as the characterization index of the correlation between the LOS channel and the NLOS channel and draw up the judgment threshold value of the correlation strength, the CDF (cumulative distribution function of the condition numbers) distribution conditions of the LOS channel and the NLOS channel are counted under 1000-frame channel simulation, as shown in FIG. 4.
In fig. 4, the abscissa represents the condition number and the ordinate represents the cumulative distribution function CDF of the condition number, and in fig. 4, three channels are shown, which are respectively a non line-of-sight channel (LET-Hi NLOS), a line-of-sight channel (LET-Hi LOS), and an Ideal dual antenna transmit/receive transmission mode (Ideal 2 × 2MIMN channel), where LET-Hi is a technology that uses a linear energy transfer small base station to meet the requirements of hot spots and indoor coverage. As can be seen from fig. 4, in an ideal case, the cumulative distribution function distribution of the condition numbers is stable, and in an actual case, the larger the condition number is, the more suitable the channel type is LOS, and the smaller the condition number is, the more suitable the channel type is NLOS. Since TM3 gains gain by using the irrelevancy between antennas, it is not suitable for the LOS channel environment, especially for the dynamic channel condition, where LOS and NLOS are in continuous switching, so it is necessary to perform transmission mode adaptation.
In an optional embodiment of the present invention, after determining the channel type of the current frame corresponding to the determination result and determining the transmission mode of the current frame according to the channel type, the transmission mode of the current frame may be further used as the transmission mode corresponding to a frame in a preset period adjacent to the current frame.
Specifically, if the corresponding transmission mode is determined for each frame, and then the corresponding transmission mode is adopted for the channel environment corresponding to each frame, the throughput performance of the link can be greatly improved. However, in practice, if there are many adjacent frames with different transmission modes, the transmission mode needs to be adjusted continuously, which causes extra bandwidth loss to the system. In order to reduce the extra bandwidth loss caused by continuous adjustment to the system, a proper adjustment period is often selected for adaptive adjustment, and for the adaptive method described in the present invention, a period that is the same as a CQI (channel quality Indicator) report may be adopted, or a period value that better meets the actual requirement may be determined through an experiment, for example, twenty frames may be a period, and when it is determined that the transmission mode of the current frame is spatial multiplexing, the transmission modes of nineteen frames adjacent to the current frame are also spatial multiplexing. Here, the transmission mode of the current frame is used as the transmission mode corresponding to the frame in the preset period adjacent to the current frame, so that the extra bandwidth loss caused by the system can be reduced, wherein the preset period is set according to the actual requirement.
Another schematic flow chart of a transmission mode adaptive method based on inter-channel correlation according to an embodiment of the present invention is shown in fig. 5, and the specific process is as follows:
Here, since it is necessary to determine a corresponding transmission mode for the nth frame, a signal of the nth frame, which may be any one frame in the entire channel, needs to be received at the receiving end.
Step 502, obtaining a matrix H through channel estimation, and performing SVD on the matrix H.
Here, since the present invention judges the channel type of the nth frame by the condition number, the condition number is obtained by singular value decomposition. Therefore, it is necessary to perform channel estimation on the nth frame to obtain a matrix H, which is a channel matrix, and perform singular value (SDV) decomposition on the channel matrix to obtain a diagonal matrix, where elements in the diagonal matrix are singular values of the channel matrix.
The diagonal matrix obtained by performing singular value (SDV) decomposition on the channel matrix comprises a plurality of singular values, and the ratio of the maximum singular value to the minimum singular value in the singular values is used as the Condition Number (CN) of the current frame.
Here, CNT is a preset condition number threshold value, and a judgment result is obtained by judging whether the condition number CN of the current frame is greater than the preset condition number threshold value CNT.
Specifically, when the condition number is greater than the preset condition number threshold value, it is determined that the channel type of the current frame corresponding to the determination result is the LOS channel, and a space diversity transmission mode is adopted for the LOS channel.
Specifically, when the condition number is less than or equal to the preset condition number threshold value, the channel type of the current frame corresponding to the judgment result is determined to be the NLOS channel, and a spatial multiplexing transmission mode is adopted for the NLOS channel.
In step 507, the transmission mode of the next frame is determined.
And after the transmission mode of the Nth frame is determined, adopting the transmission mode for the Nth frame, and continuously determining the transmission mode of the (N + 1) th frame in the same way as the step for determining the Nth frame.
It can be seen that, in the transmission mode adaptive method based on correlation between channels provided in the embodiments of the present invention, channel estimation is performed on the nth frame of the receiving end to obtain a channel matrix; obtaining a diagonal matrix by performing singular value decomposition on the channel matrix; then calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the condition number of the Nth frame; judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the Nth frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, thereby greatly improving the throughput performance of the link.
The transmission mode self-adaptive method based on the correlation between the channels provided by the embodiment of the invention is adopted for simulation, the resource size is 2PRBs, and high-order 256QAM is adopted. The relevant parameters are shown in table 1.
TABLE 1
Wherein, RB represents antenna bearer, HARQ represents hybrid automatic repeat request, QPSK represents quadrature phase shift keying signal, AMC represents adaptive modulation and coding, and MMSE represents parallel minimum mean square error algorithm.
Simulation results as shown in fig. 6, the simulation results given in fig. 6 show that the abscissa represents the signal-to-noise ratio (SNR) in decibels (dB), the ordinate represents the Throughput of the link (Throughput) in megabits per second (Mbps). The simulation results of the spatial diversity under the line of sight, the simulation results of the spatial multiplexing under the line of sight, the simulation results of the spatial diversity under the non-line of sight, the simulation results of the spatial multiplexing under the non-line of sight, the simulation results of the transmission mode adaptation of the line of sight, and the simulation results of the transmission mode adaptation of the non-line of sight are shown in the figure. As can be seen from fig. 6, after transmission mode adaptation is performed, the most suitable transmission mode is selected among TM2 (spatial diversity) and TM3 (spatial multiplexing) at line-of-sight and non-line-of-sight, compared to when no adaptation is performed, thereby maximizing the throughput performance of the link.
Referring to fig. 7, fig. 7 is a schematic structural diagram of a transmission mode adaptive apparatus based on inter-channel correlation according to an embodiment of the present invention, including the following modules:
an estimating module 701, configured to perform channel estimation on a current frame at a receiving end to obtain a channel matrix;
a decomposition module 702, configured to perform singular value decomposition on the channel matrix to obtain a diagonal matrix, where a diagonal element in the diagonal matrix is a singular value of the channel matrix;
a calculating module 703, configured to calculate a ratio of a maximum singular value to a minimum singular value in all singular values, where the ratio is used as a condition number of a current frame, and the condition number represents the magnitude of correlation between channels;
the determining module 704 is configured to determine whether the condition number is greater than a preset condition number threshold, obtain a determination result, determine a channel type of the current frame corresponding to the determination result, and determine a transmission mode of the current frame according to the channel type, where the channel type includes a line-of-sight (LOS) channel or a non-NLOS channel.
Therefore, according to the transmission mode adaptive device based on the correlation between channels provided by the embodiment of the invention, channel estimation is firstly carried out on a current frame at a receiving end through an estimation module to obtain a channel matrix; then, singular value decomposition is carried out on the channel matrix through a decomposition module to obtain a diagonal matrix; calculating the ratio of the maximum singular value to the minimum singular value in all singular values through a calculation module, and taking the ratio as the condition number of the current frame; and finally, judging whether the condition number is larger than a preset condition number threshold value through a judging module to obtain a judging result, determining the channel type of the current frame corresponding to the judging result, and determining the transmission mode of the current frame according to the channel type. The condition number is used as the correlation index between channels, the size of the condition number of the current frame and the preset condition number threshold value is judged, whether the current frame is an LOS channel type or an NLOS channel type is determined according to the judgment result, and finally the transmission mode of the current frame is determined according to the channel type, so that the throughput performance of a link is greatly improved.
Further, the decomposition module 702 is specifically configured to:
according to the formula
Performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein m × m, m × n and n × n respectively represent the rank of the matrix, m represents the number of transmitting-end antennas, n represents the number of receiving-end antennas, H represents the channel matrix, U represents a left unitary matrix, U1, …, Um, … and U represent unitary matrices, and the channel matrix is divided into m × m, m × n and n × nm(m-1)+1，…，Um×mRespectively, elements of the left unitary matrix, S denotes a diagonal matrix, S1, …, Sm × n respectively, elements of the diagonal matrix, denote singular values of the channel matrix, H denotes a right unitary matrix, V1, …, Vn, …, Vn(n-1)+1，…，Vn×nRespectively, elements of the left unitary matrix.
Further, the determining module 704 includes:
the judgment submodule is used for judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result;
the first determining submodule is used for determining that the channel type of the current frame corresponding to the judgment result is an LOS channel and adopting a space diversity transmission mode for the LOS channel if the judgment result is that the condition number is larger than a preset condition number threshold value;
and the second determining submodule is used for determining that the channel type of the current frame corresponding to the judgment result is an NLOS channel and adopting a spatial multiplexing transmission mode for the NLOS channel if the judgment result shows that the condition number is smaller than or equal to the preset condition number threshold value.
Further, the apparatus further comprises:
and the determining module is used for taking the transmission mode of the current frame as the transmission mode corresponding to the frame in the adjacent preset period after the current frame.
An embodiment of the present invention further provides an electronic device, as shown in fig. 8, which includes a processor 801, a communication interface 802, a memory 803, and a communication bus 804, where the processor 801, the communication interface 802, and the memory 803 complete mutual communication through the communication bus 804,
a memory 803 for storing a computer program;
the processor 801 is configured to implement the following steps when executing the program stored in the memory 803:
performing channel estimation on a current frame of a receiving end to obtain a channel matrix;
performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein diagonal elements in the diagonal matrix are singular values of the channel matrix;
calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, taking the ratio as the condition number of the current frame, and representing the magnitude of the correlation between the channels by the condition number;
judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, wherein the channel type comprises a line-of-sight (LOS) channel or a non-NLOS channel.
The communication bus mentioned in the electronic device may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The communication bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown, but this does not mean that there is only one bus or one type of bus.
The communication interface is used for communication between the electronic equipment and other equipment.
The Memory may include a Random Access Memory (RAM) or a Non-Volatile Memory (NVM), such as at least one disk Memory. Optionally, the memory may also be at least one memory device located remotely from the processor.
The Processor may be a general-purpose Processor, including a Central Processing Unit (CPU), a Network Processor (NP), and the like; but may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component.
Therefore, according to the electronic device provided by the embodiment of the invention, channel estimation is firstly carried out on the current frame of the receiving end to obtain a channel matrix; then, singular value decomposition is carried out on the channel matrix to obtain a diagonal matrix; then calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the condition number of the current frame; and finally, judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type. The condition number is used as the correlation index between channels, the size of the condition number of the current frame and the preset condition number threshold value is judged, whether the current frame is an LOS channel type or an NLOS channel type is determined according to the judgment result, and finally the transmission mode of the current frame is determined according to the channel type, so that the throughput performance of a link is greatly improved.
In yet another embodiment of the present invention, a computer-readable storage medium is further provided, which stores instructions that, when executed on a computer, cause the computer to perform a transmission mode adaptation method based on inter-channel correlation as described in any one of the above embodiments. The transmission mode self-adapting method based on the correlation between the channels comprises the following steps:
performing channel estimation on a current frame of a receiving end to obtain a channel matrix;
performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein diagonal elements in the diagonal matrix are singular values of the channel matrix;
calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, taking the ratio as the condition number of the current frame, and representing the magnitude of the correlation between the channels by the condition number;
judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, wherein the channel type comprises a line-of-sight (LOS) channel or a non-NLOS channel.
Therefore, with the computer-readable storage medium provided by the embodiment of the present invention, channel estimation is performed on a current frame at a receiving end to obtain a channel matrix; then, singular value decomposition is carried out on the channel matrix to obtain a diagonal matrix; then calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the condition number of the current frame; and finally, judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type. The condition number is used as the correlation index between channels, the size of the condition number of the current frame and the preset condition number threshold value is judged, whether the current frame is an LOS channel type or an NLOS channel type is determined according to the judgment result, and finally the transmission mode of the current frame is determined according to the channel type, so that the throughput performance of a link is greatly improved.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the embodiments of the apparatus, the electronic device, and the computer-readable storage medium, since they are substantially similar to the embodiments of the method, the description is simple, and for the relevant points, reference may be made to the partial description of the embodiments of the method.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.
Claims (8)
1. A method for transmission mode adaptation based on inter-channel correlation, the method comprising:
performing channel estimation on a current frame of a receiving end to obtain a channel matrix;
performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein diagonal elements in the diagonal matrix are singular values of the channel matrix;
calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, and taking the ratio as the condition number of the current frame, wherein the condition number represents the correlation size between channels;
judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, wherein the channel type comprises a line-of-sight (LOS) channel or a non-NLOS channel;
the judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result, determining the channel type of the current frame corresponding to the judgment result, and determining the transmission mode of the current frame according to the channel type, includes:
judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result;
if the judgment result is that the condition number is larger than the preset condition number threshold value, determining that the channel type of the current frame corresponding to the judgment result is the LOS channel, and adopting a space diversity transmission mode for the LOS channel;
and if the judgment result is that the condition number is smaller than or equal to the preset condition number threshold value, determining that the channel type of the current frame corresponding to the judgment result is the NLOS channel, and adopting a spatial multiplexing transmission mode for the NLOS channel.
2. The method of claim 1, wherein the performing a singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein diagonal elements in the diagonal matrix represent singular values of the channel matrix, comprises:
according to the formula
Performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein m × m, m × n and n × n respectively represent the rank of the matrix, m represents the number of transmitting-end antennas, n represents the number of receiving-end antennas, H represents the channel matrix, U represents a left unitary matrix, U1, …, Um, … and U represent unitary matrices, and the channel matrix is divided into m × m, m × n and n × nm(m-1)+1，…，Um×mRespectively, elements of the left unitary matrix, S denotes a diagonal matrix, S1, …, Sm × n respectively, elements of the diagonal matrix, denote singular values of the channel matrix, H denotes a right unitary matrix, V1, …, Vn, …, Vn(n-1)+1，…，Vn×nRespectively, elements of the left unitary matrix.
3. The method according to claim 1, wherein after determining the channel type of the current frame corresponding to the determination result and determining the transmission mode of the current frame according to the channel type, the method further comprises:
and taking the transmission mode of the current frame as the transmission mode corresponding to the frame in the adjacent preset period after the current frame.
4. An apparatus for transmission mode adaptation based on inter-channel correlation, the apparatus comprising:
the estimation module is used for carrying out channel estimation on the current frame of the receiving end to obtain a channel matrix;
the decomposition module is used for carrying out singular value decomposition on the channel matrix to obtain a diagonal matrix, and diagonal elements in the diagonal matrix are singular values of the channel matrix;
the calculation module is used for calculating the ratio of the maximum singular value to the minimum singular value in all the singular values, taking the ratio as the condition number of the current frame, and the condition number represents the size of the correlation between channels;
the judging module is used for judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judging result, determining the channel type of the current frame corresponding to the judging result, and determining the transmission mode of the current frame according to the channel type, wherein the channel type comprises a line-of-sight (LOS) channel or a non-line-of-sight (NLOS) channel;
the judging module comprises:
the judgment submodule is used for judging whether the condition number is larger than a preset condition number threshold value or not to obtain a judgment result;
a first determining submodule, configured to determine that the channel type of the current frame corresponding to the determination result is the LOS channel and apply a space diversity transmission mode to the LOS channel if the determination result indicates that the condition number is greater than the preset condition number threshold value;
and a second determining submodule, configured to determine that the channel type of the current frame corresponding to the determination result is the NLOS channel and adopt a spatial multiplexing transmission mode for the NLOS channel, if the determination result indicates that the condition number is smaller than or equal to the preset condition number threshold value.
5. The apparatus of claim 4, wherein the decomposition module is specifically configured to:
according to the formula
Performing singular value decomposition on the channel matrix to obtain a diagonal matrix, wherein m × m, m × n and n × n respectively represent the rank of the matrix, m represents the number of transmitting-end antennas, n represents the number of receiving-end antennas, H represents the channel matrix, U represents a left unitary matrix, U1, …, Um, … and U represent unitary matrices, and the channel matrix is divided into m × m, m × n and n × nm(m-1)+1，…，Um×mRespectively of said left unitary matrixElements, S denotes a diagonal matrix, S1, …, Sm × n are elements of the diagonal matrix, respectively, representing singular values of the channel matrix, H denotes a right unitary matrix, V1, …, Vn, …, Vn(n-1)+1，…，Vn×nRespectively, elements of the left unitary matrix.
6. The apparatus of claim 4, further comprising:
and the determining module is used for taking the transmission mode of the current frame as the transmission mode corresponding to the frame in the adjacent preset period after the current frame.
7. An electronic device, comprising a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory complete communication with each other through the communication bus;
the memory is used for storing a computer program;
the processor, when executing the program stored in the memory, implementing the method steps of any of claims 1-3.
8. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the method steps of any one of claims 1 to 3.
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