RU2490797C2 - Adaptive switching method and system for downlink multiple input multiple output mode - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: when the decision moment is arriving, the wireless communication system decides that the MIMO mode suitable for use in a receiver is spatial multiplexing mode or spatial diversity mode according to the channel information, and according to the decision result, data are transmitted using the corresponding MIMO mode between the transmitter end and the receiver. The channel information includes any one or more of the following: signal-to-noise ratio, modulation and coding mode and condition number of channel matrix.

EFFECT: high reliability of communication lines and high capacity of the system.

42 cl, 12 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to the field of wireless communications, and in particular, to a method and system for adaptive switching modes with multiple inputs and multiple outputs (MIMO, Multiple Input Multiple Output) in the downlink.

BACKGROUND

MIMO technology (Multiple-Input Multiple-Output, multiple inputs and multiple outputs) is one of the key technologies that should be used in the next generation mobile communication system. Since many antennas are used in both the receiver and the transmitter, this technology has undeniable advantages over technologies involving the use of one antenna for reception and one antenna for transmission. Using this technology, multipath attenuation can be attenuated by using multiple paths, effectively eliminating intra-channel interference and improving channel reliability, as well as increasing the throughput of a communication system without extending the bandwidth.

There are two main applications of MIMO technology - spatial diversity and spatial multiplexing. Moreover, diversity can increase the reliability of communication lines and expand the coverage area. If the coverage area and the requirements for the frequency of bit errors in the receiver are fixed, the gain achieved as a result of diversity can lead to an increase in the data rate. Multiplexing allows you to transmit different data through each antenna, so you can improve spectral efficiency, as well as increase the data transfer rate. Due to the mobility of the receiver and the real-time change of the wireless channel, a higher data rate can be obtained by using the diversity mode at certain points, while at other times it can be obtained by using the spatial multiplexing mode. Thus, the limited frequency range cannot be fully utilized only by separately using diversity technology or multiplexing technology.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is the need to implement a method and system for adaptive switching modes with multiple inputs and multiple outputs (MIMO) in the downlink, which allow you to adaptively switch between modes of spatial diversity and spatial multiplexing, so that they are effectively Combine and, thus, increase the reliability of communication lines and increase the throughput of the system.

In order to solve the above problem, the present invention provides a method for adaptive multi-input multi-output (MIMO) downlink mode switching applicable to a wireless communication system comprising a transmitter and a receiver, the method includes:

when the decision is made, the wireless system, in accordance with the channel information, decides that the MIMO mode suitable for use in the receiver is a spatial multiplex mode or a spatial diversity mode; data transmission between the transmitter and the receiver in the corresponding MIMO mode according to the decision;

wherein the channel information includes one or more of the following: signal-to-noise ratio, modulation and coding mode, and the condition number of the channel matrix.

In addition, the step by which a wireless communication system decides on a MIMO mode suitable for use in a receiver in accordance with channel information includes:

returning channel information by the receiver to the transmitter, deciding by the transmitter on the MIMO mode suitable for use in the receiver in accordance with the channel information returned by the receiver, and informing the receiver of the selected MIMO mode after selecting the MIMO mode to be used in accordance with decision made; or

the receiver deciding on the MIMO mode suitable for use in the receiver in accordance with the received channel information and informing the transmitter of the selected MIMO mode after selecting the MIMO mode to be used in accordance with the decision.

In addition, the transmitter is a base station, and the receiver includes a terminal, a base station, or a relay station.

In addition, the step of making the wireless communication system, in accordance with the channel information, the decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes, in particular, the following steps:

calculation by the wireless communication system of spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and determining a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver.

In addition, the step of calculating the spectral efficiency by the wireless communication system in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information includes, in particular, the following steps:

calculating the STC_CINR signal-to-noise ratio for each receiver antenna of the receiver in the spatial diversity mode, determining a modulation and coding mode suitable for the spatial diversity mode in accordance with the STC_CINR ratio and determining the modulation and coding order, the coding rate, and the number of coding repetitions in accordance with the mode modulation and coding; calculating the spectral efficiency for each receiving antenna by multiplying the modulation order and coding in the spatial diversity mode by the coding rate and then dividing by the number of coding repetitions, and combining the spectral efficiency values of each receiving antenna to obtain the spectral efficiency of the receiver in the spatial diversity mode; and

calculating the signal-to-noise ratio SM_CINR for each receiving antenna of the receiver in spatial multiplexing mode, determining a modulation and coding mode suitable for the spatial multiplexing mode in accordance with the SM_CINR ratio and determining the modulation and coding order, coding rate and number of coding repetitions in spatial multiplexing mode in accordance with the modulation and coding mode; calculating the spectral efficiency for each receiving antenna by multiplying the modulation order and coding in spatial multiplexing mode by the coding rate and then dividing by the number of coding repetitions, and combining the spectral efficiency values of each receiving antenna to obtain the spectral efficiency of the receiver in spatial multiplexing mode.

In addition, the step of deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in the receiver includes the following steps:

if the spectral efficiency value of the SM_Effect receiver in the spatial multiplexing mode is greater than the spectral efficiency of the receiver STC_Effect in the spatial diversity mode, decide that the spatial multiplexing mode is suitable for use in the receiver, otherwise, decide which is suitable for use in the receiver spatial diversity mode; and

if the SM_Effect value is equal to the STC_Effect value, decide that the spatial multiplex mode or spatial diversity mode is suitable for use in the receiver.

In addition, the step of making the wireless communication system, in accordance with the channel information, a decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes the following steps:

determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver.

In addition, the step of determining the mode, MIMO, suitable for use on each subcarrier, according to the condition number of the channel matrix of the receiver corresponding to each subcarrier, includes the following steps:

setting a threshold value for the subcarrier;

determining a channel matrix consisting of channel coefficients corresponding to the receiver, and calculating a condition number of the channel matrix of the receiver corresponding to each subcarrier; and

comparing the condition number of the channel matrix of the receiver corresponding to each subcarrier with the corresponding threshold value for the subcarrier to determine that each subcarrier is suitable for use in the spatial diversity mode or spatial multiplexing mode.

In addition, the decision step that the particular mode is a MIMO mode suitable for use in the receiver if the ratio of subcarriers suitable for use in this mode and all subcarriers selected as statistical objects exceeds a predetermined threshold ratio value, contains the following steps:

setting the threshold value of the ratio Tr;

calculating the ratio Pr of the number of subcarriers suitable for use in the spatial multiplexing mode and the number of all subcarriers selected as statistical objects, and

if the Pr value is greater than or equal to the threshold value of the Tr ratio, deciding that the MIMO mode suitable for use in the receiver should be a spatial multiplexing mode; otherwise, the decision that the MIMO mode suitable for use in the receiver should be a spatial diversity mode.

In addition, the step of making the wireless communication system, in accordance with the channel information, a decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes the following steps:

determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; and

if the ratio of subcarriers suitable for use in the spatial multiplexing mode to all subcarriers selected as statistical objects is less than a predetermined ratio threshold, decide that the MIMO mode suitable for use in the receiver is the spatial diversity mode.

In addition, the method also includes:

setting the threshold value of the ratio Tr and

calculating the ratio Pr of the number of subcarriers suitable for use in the spatial multiplexing mode and the number of all subcarriers selected as statistical objects; and

in this case, if the ratio of subcarriers suitable for use in the spatial multiplexing mode is less than a predetermined threshold value of the ratio, this means that the value of Pr is less than the value of Tr.

The method also includes:

calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if the Pr value is greater than or equal to the Tr value; and deciding that the MIMO mode with greater spectral efficiency should be the MIMO mode suitable for use by the receiver.

The method also includes:

setting another threshold value of the relation T _r2 , with 0≤T _r ≤T _r2 ≤1;

if Pr> T _r2 , deciding that the spatial multiplexing mode is suitable for use in the receiver; and

if T _r ≤Pr≤T _r2 , calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver.

The method also includes the following steps in the process of making the wireless communication system, in accordance with the channel information, decide that the MIMO mode suitable for use in the receiver is spatial multiplexing mode or spatial diversity mode:

calculating the CINR signal-to-noise ratio in the MIMO mode currently used at the receiver;

if the CINR value is greater than a predetermined threshold ratio value, deciding that the spatial multiplexing mode is suitable for use; and

if the CINR value is less than a predetermined correlation threshold value, decide that the spatial diversity mode is suitable for use.

Moreover, the predetermined threshold value of the ratio is within the interval [CINR1, CINR2], with CINR1≤CINR; and if the CINR becomes greater than a predetermined ratio threshold, this means that CINR> CINR2; and if CINR becomes less than a predetermined threshold value of the ratio, this means that CINR <CINR1.

The method also includes:

Deciding that the current MIMO mode is suitable for use if CINR1≤CINR≤CINR2. The method also includes:

calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if CINR1 ≤ CINR C CINR2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver.

The method also includes:

determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if CINR1≤CINR≤CINR2; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver.

Moreover, for the receiver using the spatial diversity mode at the current time, the predetermined threshold value of the ratio is within the interval [STC_TH _CINR 1, STC_TH _CINR 2], wherein STC_TH _CINR 1≤STC_TH _CINR 2;

for a receiver using the spatial multiplexing mode at the current time, the predetermined threshold value of the ratio is within the interval [SM_TH _CINR 1, SM_TH _CINR 2], with SM_TH _CINR 1≤SM_TH _CINR 2; SM_TH _CINR 1≤STC_TH _CINR 2;

for a receiver using the spatial diversity mode at the current time, the CINR value exceeding the predetermined threshold value of the ratio means that CINR> STC_TH _CINR 2; reducing CINR to a value less than a predetermined threshold value of the ratio means that CINR <STC_TH _CINR 1; and

for a receiver using the spatial multiplexing mode at the current time, the CINR value exceeding a predetermined proportional threshold value means that CINR> SM_TH _CINR 2; reducing CINR to a value less than a predetermined threshold value of the ratio means that CINR <SM_TH _CINR 1.

The method also includes:

for a receiver currently using a spatial diversity mode, deciding that a spatial diversity mode is suitable for use if STC_TH _CINR 1≤CINR≤STC_TH _CINR 2; and

for a receiver that is currently using spatial multiplexing mode, deciding that spatial multiplexing mode is suitable for use if SM_TH _CINR 1≤CINR≤SM_TH _CINR 2.

The method also includes:

for a receiver currently using the spatial diversity mode, calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if STC_TH _CINR 1≤CINR≤STC_TH _CINR 2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver; and

for a receiver using the spatial multiplexing mode at the current time, calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if SM_TH _CINR 1≤CINR≤SM_TH _CINR 2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver.

The method also includes:

for a receiver currently using the spatial diversity mode, determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if STC_TH _CINR 1≤ CINR≤STC_TH _CINR 2; if the ratio of subcarriers suitable for use in a particular mode and all subcarriers selected as statistical objects exceeds a predetermined ratio threshold value, deciding that said mode is a MIMO mode suitable for use in a receiver; and

for a receiver currently using the spatial multiplexing mode, determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if SM_TH _CINR 1≤ CINR≤SM_TH _CINR 2; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver.

In addition, the step of making the wireless communication system, in accordance with the channel information, a decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes the following steps:

calculating the CINR signal-to-noise ratio in the MIMO mode currently used at the receiver; and determining a modulation and coding mode suitable for use at the receiver according to the CINR, wherein the value corresponding to the modulation and coding is DIUC;

if the DIUC value is greater than a predetermined threshold ratio value, deciding that the spatial multiplexing mode is suitable for use; and

if the DIUC value is less than a predetermined correlation threshold value, decide that the spatial diversity mode is suitable for use.

Moreover, the predetermined threshold value of the ratio is within the interval [DIUC1, DIUC2], with DIUC1≤DIUC2; and if the DIUC becomes greater than a predetermined threshold value of the ratio, this means that DIUC> DIUC2; and if DIUC becomes less than a predetermined threshold value, it means that DIUC <DIUC1.

The method also includes:

Deciding that the current MIMO mode is suitable for use if DIUC1≤DIUC≤DIUC2.

The method also includes:

calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to channel information received by the receiver if DIUC1≤DIUC≤DIUC2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver.

The method also includes:

determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if DIUC1≤DIUC≤DIUC2; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver.

The method also includes:

for a receiver using the spatial diversity mode at the current time, a predetermined threshold ratio value is within the interval [STC_TH _DIUC 1, STC_TH _DIUC 2], wherein STC_TH _DIUC 1≤STC_TH _DIUC 2;

for a receiver currently using the spatial multiplexing mode, a predetermined threshold ratio value is within the interval [SM_TH _DIUC 1, SM_TH _DIUC 2], with SM_TH _DIUC 1≤SM_TH _DIUC 2; SM_TH _DIUC 1≤STC_TH _DIUC 2;

for a receiver using the spatial diversity mode at the current time, the DIUC value exceeding the predetermined threshold value of the ratio means that DIUC> STC_TH _DIUC 2; reducing DIUC to a value less than a predetermined threshold value of the ratio means that DIUC <STC_TH _DIUC 1; and

for a receiver that is currently using spatial multiplexing mode, if the DIUC value exceeds a predetermined threshold value of the ratio, it means that DIUC> SM_TH _DIUC 2; reducing CINR to a value less than a predetermined threshold value of the ratio means that DIUC <SM_TH _DIUC 1.

The method also includes:

for a receiver currently using a spatial diversity mode, deciding that a spatial diversity mode is suitable for use if STC_TH _DIUC 1≤DIUC≤STC_TH _DIUC 2; and

for a receiver currently using the spatial multiplexing mode, deciding that the spatial multiplexing mode is suitable for use if SM_TH _DIUC 1≤DIUC≤SM_TH _DIUC 2.

The method also includes:

for a receiver currently using the spatial diversity mode, calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if STC_TH _DIUC 1≤DIUC≤STC_TH _DIUC 2; and determining a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver; and

for a receiver using the spatial multiplexing mode at the current time, calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if SM_TH _DIUC 1≤DIUC≤SM_TH _DIUC 2; and determining a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver.

The method also includes:

for a receiver currently using the spatial diversity mode, determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if STC_TH _DIUC 1≤ DIUC≤STC_TH _DIUC 2; if the ratio of subcarriers suitable for use in a particular mode and all subcarriers selected as statistical objects exceeds a predetermined ratio threshold value, deciding that said mode is a MIMO mode suitable for use in a receiver; and

for a receiver currently using the spatial multiplexing mode, determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if SM_TH _DIUC 1≤ DIUC≤SM_TH _DIUC 2; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver.

The method also includes:

determining a modulation and coding mode in the used MIMO mode in accordance with the signal-to-noise ratio, performing by the transmitter an encoding according to the determined modulation and coding mode, and performing by the receiver a decoding according to the determined modulation and coding mode.

In addition, if the signal-to-noise ratio can be determined in both MIMO modes, or the signal-to-noise ratio can only be determined in the MIMO mode used at the current time, and MIMO modes are not switched, then the step of determining the modulation and coding mode in MIMO mode, used in accordance with the signal-to-noise ratio, includes the following steps:

comparing the signal-to-noise ratio in the used MIMO mode with the threshold value of entering the modulation and coding mode and determining the modulation and coding mode in the MIMO mode.

Moreover, if only the signal-to-noise ratio in the MIMO mode used at the current time can be determined and the MIMO modes are switched, the step of determining the modulation and coding mode in the MIMO mode used in accordance with the signal-to-noise ratio includes the following Steps:

setting the differential value D_CINR between the signal-to-noise ratio in the spatial diversity mode and the signal-to-noise ratio in the spatial multiplexing mode under the same conditions, comparing the signal-to-noise ratio V_CINR in the MIMO mode currently used in the receiver with the threshold value for entering the mode modulation and coding and determining a modulation and coding mode in the MIMO mode currently in use;

calculating for the receiver using the spatial diversity mode the signal-to-noise ratio SM_CINR = V_CINR-D_CINR in the spatial multiplexing mode, comparing the SM_CINR value with a threshold value for entering the modulation and coding mode, and determining the modulation and coding mode of the receiver in the spatial multiplexing mode; and

calculating for the receiver using the spatial multiplexing mode the signal-to-noise ratio in the spatial diversity mode STC_CINR = V_CINR + D_CINR, comparing the STC_CINR value with a threshold value for entering the modulation and coding mode, and determining a modulation and coding mode of the receiver in the spatial diversity mode.

If only the signal-to-noise ratio in the MIMO mode used at the current time can be determined and the MIMO modes are switched, the step of determining the modulation and coding mode in the MIMO mode used in accordance with the signal-to-noise ratio contains the following steps:

setting the difference D between the values corresponding to the modulation and coding modes in the spatial diversity mode and in the spatial multiplexing mode, comparing the signal-to-noise ratio V_CINR in the MIMO mode currently used in the receiver with the threshold value for entering the modulation and coding mode, and determination of the modulation and coding mode in the MIMO mode used at the current time, the value corresponding to the modulation and coding mode is denoted by V_DIUC;

calculating the value SM_DIUC = V_DIUC-D corresponding to the modulation and coding mode of the receiver using the spatial diversity mode in the spatial multiplexing mode and

calculating the value STC_DIUC = V_DIUC + D corresponding to the modulation and coding mode of the receiver using the spatial multiplexing mode in the spatial diversity mode.

The method also includes:

setting the switching period T using frames as units of measurement and

preliminary specification of the moment of decision making as the moment at which the total number of transmitted / received frames is an integer multiple of T;

the step of transmitting data using the appropriate MIMO mode according to the decision includes: after deciding on the MIMO mode suitable for use, data transfer between the transmitter and receiver using this MIMO mode in the next switching period.

The method also includes:

setting a switching period T using frames as units of measurement, as well as setting a threshold value of VT, and

setting m decision decision times in each switching period, wherein m is a positive integer and m≤T;

the step of transmitting data using the appropriate MIMO mode according to the decision made includes: counting the number of STC_NUM cases when the spatial diversity mode is suitable for use, and the number of SM_NUM cases when the spatial multiplexing mode is suitable for use, in m decisions made during the current period switching, before the end of each switching period; and transmitting data between the transmitter and the receiver using the spatial multiplexing mode in the next switching period if the ratio of SM_NUM to m is greater than TH; otherwise, transmitting data using the spatial diversity mode in the next switching period.

In addition, the data transfer step using the corresponding MIMO mode according to the decision includes the following steps:

setting the threshold value of VT;

for a receiver using the spatial diversity mode, counting the number of SM_NUM cases when it is decided that the spatial multiplexing mode is suitable for use; if the ratio of SM_NUM to the total number of decision-making cases is greater than TH, switching to the spatial multiplexing mode for data transmission between the transmitter and receiver; and

for a receiver using the spatial multiplexing mode, counting the number of STC_NUM cases when it is decided that the spatial diversity mode is suitable for use; if the ratio of STC_NUM to the total number of decision cases is greater than TH, switch to spatial diversity mode to transfer data between the transmitter and receiver.

The present invention also provides a system for adaptive multi-input multi-output (MIMO) downlink mode switching, comprising: a transmitter and at least one receiver; wherein each receiver includes at least two receiving antennas, and each transmitter contains at least two transmitting antennas; each receiver is used to obtain channel information based on data received by the receiver; the transmitter comprises: a modulation and coding module for channels used for modulating and coding signals; and a symbol conversion module used to perform symbol conversion for signals output by the modulation and coding module;

wherein the transmitter or receiver at least comprise:

a mode decision module used to make decisions at certain times that the MIMO mode suitable for use in the receiver is a spatial multiplex mode or a spatial diversity mode, in accordance with channel information; and selecting the appropriate MIMO mode for use according to the decision made, as well as for informing the switching module and the receiver of the selected MIMO mode; wherein the channel information includes one or more of the following: signal-to-noise ratio, modulation and coding mode, and the condition number of the channel matrix;

The transmitter also contains:

a switching module for transmitting data from the output of the symbol conversion module to the data transmission module in the MIMO mode, the selected mode decision module;

a spatial multiplexing mode data transmission unit used to transmit data after performing spatial data multiplexing; and

a spatial diversity data transmission module used to transmit data after performing spatial data diversity;

in this case, the receiver receives data in the MIMO mode selected by the mode decision module.

In addition, the transmitter is a base station, and the receiver includes a terminal, a base station, or a relay station.

In addition, the mode decision module based on the channel information makes a decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode, as follows:

A) the calculation by the wireless communication system of spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver;

B) determining a MIMO mode suitable for use on each subcarrier, according to the condition number of the channel matrix of the receiver corresponding to each subcarrier, by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in a particular mode and all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, deciding that the specified mode is a MIMO mode suitable for use in the receiver;

C) determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in spatial multiplexing mode to all subcarriers selected as statistical objects is less than a predetermined ratio threshold value, a decision is made that the MIMO mode suitable for use in the receiver is spatial diversity mode, in Otherwise, perform one of the following two steps:

C1) if the ratio of subcarriers suitable for use in the spatial multiplexing mode is greater than another predetermined threshold value of the ratio, deciding that the MIMO mode suitable for use in the receiver is the spatial multiplexing mode, otherwise, performing step C2;

C2) calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver;

D) calculating the CINR signal-to-noise ratio in the MIMO mode currently used at the receiver; if the CINR is greater than the first predetermined ratio threshold value, deciding that the spatial multiplexing mode is suitable for use; and if the CINR is less than the second predetermined threshold value of the ratio, deciding that the spatial diversity mode is suitable for use; if the CINR value is less than or equal to the first predetermined ratio threshold value and greater than or equal to the second predetermined ratio threshold value, perform one of the following two steps.

D1) calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver, or

D2) determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in a particular mode and all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, deciding that the specified mode is a MIMO mode suitable for use in the receiver;

E) calculating the CINR signal-to-noise ratio in the MIMO mode currently used at the receiver; determining a modulation and coding mode suitable for use at the receiver according to CINR, wherein the value corresponding to modulation and coding is DIUC; if the DIUC is greater than the first predetermined threshold value of the ratio, deciding that the spatial multiplexing mode is suitable for use; if the DIUC is less than a second predetermined threshold value of the ratio, deciding that the spatial diversity mode is suitable for use; if the DIUC value is less than or equal to the first predetermined ratio threshold value and greater than or equal to the second predetermined ratio threshold value, perform one of the following two steps:

E1) calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver, or

E2) determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined correlation threshold value, decide that the specified mode is a MIMO mode suitable for use in the receiver.

In addition, the transmitter or receiver also includes: a modulation and coding mode tuning module used to configure a modulation and coding mode used by the modulation and coding module as a mode suitable for use in the receiver in accordance with the MIMO mode selected by the decision module About the mode in one of the following ways:

a) if the signal-to-noise ratio can be determined in both MIMO modes or the signal-to-noise ratio can only be determined in the MIMO mode used at the current moment in time, and MIMO modes are not switched, performing signal-to-noise comparison in the mode MIMO used at the current time, with a threshold value of entering the modulation and coding mode and determining the modulation and coding mode in the MIMO mode;

b) if only the signal-to-noise ratio in the MIMO mode used at the current time can be determined and the MIMO modes are switched, setting the difference value D_CINR between the signal-to-noise ratio in the spatial diversity mode and the signal-to-noise ratio in the spatial multiplexing mode at the same conditions, comparing the signal-to-noise ratio V_CINR in the MIMO mode currently used in the receiver with the threshold value for entering the modulation and coding mode and determining the modulation mode and dying in the MIMO mode currently in use; calculating the signal-to-noise ratio SM_CINR = V_CINR-D_CINR for a receiver using the spatial diversity mode in the spatial multiplexing mode, comparing the SM_CINR value with a threshold value for entering the modulation and coding mode, and determining a modulation and coding mode of the receiver in the spatial multiplexing mode; and computing the signal-to-noise ratio STC_CINR = V_CINR + D_CINR for a receiver using the spatial multiplexing mode in the spatial diversity mode, comparing the STC_CINR value with a threshold value for entering the modulation and coding mode and determining a modulation and coding mode of the receiver in the spatial diversity mode; and

c) if only the signal-to-noise ratio can be determined in the MIMO mode currently in use, and the MIMO modes are switched, the difference D is set between the values corresponding to the modulation and coding modes in the spatial diversity mode and in the spatial multiplexing mode, comparing the ratio signal / noise V_CINR in the MIMO mode currently used in the receiver, with a threshold value for entering the modulation and coding mode and determining the modulation and coding mode in the MIMO mode, used at the current time, and the value corresponding to the modulation mode and coding is denoted by V_DIUC; calculating the value SM_DIUC = V_DIUC-D corresponding to the modulation and coding mode of the receiver using the spatial diversity mode in the spatial multiplexing mode; and calculating the value STC_DIUC = V_DIUC + D corresponding to the modulation and coding mode of the receiver using the spatial multiplexing mode in the spatial diversity mode.

In addition, the transmitter or receiver also contains a configuration module for configuring the moment of making a decision about the MIMO mode, while the configuration module is also used to:

i) setting the switching period T using frames as units of measurement, and

wherein the configuration module sets the decision point at which the MIMO mode is determined as the moment when the total number of transmitted / received frames is an integer multiple of T; and the mode decision module selecting the appropriate MIMO mode for use according to the decision made, does the following: after deciding on a suitable MIMO mode for use, the mode decision module selects the MIMO mode for use;

ii) setting the switching period T using frames as units of measurement,

wherein the configuration module sets m decision decision times in each switching period, wherein m is a positive integer and m≤T; a mode decision module that selects the appropriate MIMO mode to use according to the decision, performs the following: counts the number of STC_NUM and SM_NUM cases suitable for using the spatial diversity mode and spatial multiplexing mode in m decisions during the current switching period until the end of each switching period; selects a spatial multiplexing mode for use in the next switching period if the ratio SM_NUM to m is greater than a predetermined threshold TH; otherwise, selects a spatial diversity mode for use in the next switching period; or

iii) configuring the decision point,

wherein the mode decision module selecting the appropriate MIMO mode for use according to the decision made does the following: for a receiver using the spatial diversity mode, it counts the number of SM_NUM cases when it is decided that the spatial multiplexing mode is suitable for use; if the ratio of SM_NUM to the total number of decision cases is greater than a predetermined threshold value of the VT, selects the spatial multiplexing mode for receiving data to use; for a receiver using the spatial multiplexing mode, counts the number of STC_NUM cases when it is decided that the spatial diversity mode is suitable for use; if the ratio of STC_NUM to the total number of decision cases is greater than the VT, selects the spatial diversity mode for use.

The technical solution proposed in the present invention allows to solve the problem of performing adaptive switching between spatial diversity and spatial multiplexing modes in a system with multiple downlink antennas and efficient use of diversity gain, as well as increasing the data rate due to spatial multiplexing, As a result, system throughput is significantly increased. A large number of simulation results show that the technical solution proposed in the present invention can increase the system throughput by 10% -20%.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a block diagram for deciding on a MIMO mode based on spectral efficiency in accordance with the present invention.

Figure 2 shows a block diagram for deciding a MIMO mode based on a condition number in accordance with the present invention.

Figure 3 shows a block diagram for deciding on a MIMO mode based on a signal to noise ratio or modulation and coding value in accordance with the present invention.

4 (a), (b) and (c) show three specific methods for selecting a MIMO mode based on the decision made.

5 illustrates a transmitter comprising a mode decision module and a modulation and coding mode module.

FIG. 6 is a flowchart for deciding on a MIMO mode and directly tuning a portion of a-CINR DIUC in accordance with a first example application of the present invention.

7 is a flowchart for a receiver to decide on a MIMO mode in spatial diversity mode based on CINR and spectral efficiency in accordance with a second application example of the present invention.

On Fig shows the channel coefficient corresponding to the i-th subcarrier of the receiver, in accordance with the third application example of the present invention.

9 is a flowchart for making decisions based on condition number and spectral efficiency in accordance with a third application example of the present invention.

10 is a flowchart for a receiver to make a decision about a suitable MIMO mode by counting during a switching period based on spectral efficiency in accordance with a fourth application example of the present invention.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

Below with reference to the drawings and examples, the technical solution of the implementation of the present invention is described in detail.

The present invention is proposed in light of the consideration of the following factors.

To maximize the data transfer rate, the combined use of spatial diversity and spatial multiplexing modes is taken into account. In other words, the system uses channel information to determine the rules for switching MIMO modes and performs adaptive switching between different modes with multiple antennas in such a way as to increase the reliability of the communication line and increase the throughput of the system. The main idea is to select a MIMO mode using channel information and adjust the modulation and coding mode suitable for the selected MIMO mode to transmit data in the MIMO mode selected by the decision module.

A method for implementing adaptive downlink MIMO switching in accordance with the present invention is applicable to a wireless communication system comprising a transmitter and a receiver. The method includes:

when the decision is made, the wireless system, in accordance with the channel information, decides that the MIMO mode suitable for use in the receiver is a spatial multiplex mode or a spatial diversity mode; data transmission between the transmitter and the receiver in the corresponding MIMO mode according to the decision;

channel information includes one or more of the following: signal to noise ratio, modulation and coding mode, and condition number of the channel matrix

The moment of decision-making is set in advance in accordance with a specific situation, for example, a decision is made every time data is received / transmitted, or through several data transmission / reception sessions, or in each frame.

For different receivers, the appropriate MIMO modes may vary, while the decision method to be used is usually the same, but in some cases, for example, when the decision on the mode is made at the receiver, different receivers may use different decision methods.

Signal to noise ratio is a general term denoted by the abbreviation SNR (Signal to Noise Ratio); this term may refer to the ratio of signal level to interference and noise (SINR, Signal to Interference and Noise Ratio) or the ratio of carrier level to interference and noise (CINR, Carrier to Interference plus Noise Ratio); in the following description, various signal-to-noise ratios, including SNR and SINR, will be generically denoted by the acronym CINR.

The value corresponding to the modulation and coding mode is called for brevity the modulation and coding value, and the DIUC code (Downlink Interval Usage Code) in accordance with the 802.16 standard can also be used several times to indicate this value in the following description to simplify it.

At the same time, the basic means of a wireless communication system that decide which MIMO mode is suitable for use, in accordance with the channel information, should determine the rules or algorithm for deciding on the MIMO mode; moreover, the decision on the MIMO mode can be made in two ways: in the first case, the decision is made at the transmitter, while the receiver must return the channel information to the transmitter, and the transmitter decides on the MIMO mode suitable for use in the receiver, in accordance with the channel information returned receiver, and informs the receiver of the selected MIMO mode after selecting the MIMO mode that you want to use, in accordance with the decision. In the second case, the decision is made at the receiver, while the receiver decides on the MIMO mode suitable for use in accordance with the received channel information, and informs the transmitter about the selected MIMO mode after selecting the MIMO mode that must be used in accordance with the received decision. The opposite side can also undoubtedly be notified of the decision made immediately after making this decision, after which the transmitter and the receiver, based on the same rules, select the MIMO mode, which must be used in accordance with the decision.

Moreover, the transmitter includes a base station, etc., but is not limited to, and the receiver includes terminal equipment such as a mobile phone, laptop computer, data card and personal digital assistant (PDA), base station or relay station, etc. ., but not limited to the above.

Depending on the differences in the channel information, the method for deciding the suitable MIMO mode in accordance with the channel information includes at least the following:

(A1) decision making in accordance with spectral efficiency.

Comparing the spectral efficiency in the spatial diversity mode with the spectral efficiency in the spatial multiplexing mode and deciding on the MIMO mode with greater spectral efficiency as the MIMO mode suitable for use in the receiver. This process can be implemented as follows.

The CINR ratio of each receiving antenna of each receiver in the spatial diversity mode, which is denoted as STC_CINR, is calculated, then the CINR of each receiving antenna in the spatial multiplexing mode, which is denoted as SM_CINR, is calculated, thus the CINR ratio of each receiver in two MIMO modes is determined. A modulation and coding mode suitable for the MIMO mode can be determined in accordance with STC_CINR and SM_CINR, and values corresponding to the modulation and coding modes of the receiver in the spatial diversity mode and in the spatial multiplexing mode are recorded as STC_DIUC and SM_DIUC, respectively. The modulation and coding order, coding rate, and number of coding repetitions can be determined using STC_DIUC and SM_DIUC, which determines the spectral efficiency of each receiving antenna in the corresponding MIMO mode. In this case, spectral efficiency = modulation and coding order × coding rate / number of coding repetitions. The spectral efficiency values of each receiver receive antenna are combined to obtain the total spectral efficiency of the receiver. Other methods can undoubtedly also be used to calculate spectral efficiency in specific applications.

The total spectral efficiency of the receiver in the spatial diversity mode and in the spatial multiplexing mode is referred to as STC_Effect and SM_Effect. If the value of SM_Effect is greater than (or equal to) the value of STC_Effect, then a decision is made that the spatial multiplexing mode is suitable for use in the receiver; otherwise, a decision is made that the diversity mode is suitable for use in the receiver. In other words, if the value of SM_Effect is equal to the value of STC_Effect, then it may be decided that the spatial multiplexing mode is suitable for use in the receiver, or it may be decided that the spatial diversity mode is suitable for use in the receiver; a decision can even be made based on other channel information. This process is shown in FIG. 1, where the STC corresponds to the spatial diversity mode, while the SM corresponds to the spatial multiplexing mode.

(A2) Decision making according to conditionality number

Determining the MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined threshold value for the ratio, the decision is made that this mode is a MIMO mode suitable for use in the receiver.

This process can be implemented as follows.

First, a conditional number of the channel matrix corresponding to each subcarrier is calculated and a conditionality number is compared with a predetermined threshold value for the subcarrier, whereby it is determined which mode is suitable for using the subcarrier — the spatial diversity mode or the spatial multiplexing mode. Collecting statistics on all or part of the receiver subcarriers, if the ratio of the subcarriers for which a particular mode is suitable and the total number of subcarriers selected as statistical objects is greater than or equal to a predetermined threshold value of the ratio, then a decision is made that this mode is suitable for subcarrier usage; otherwise, deciding that another mode is suitable for use. The decision can also be made in other ways. In specific applications, the decision can be made as follows: if the ratio of the subcarriers for which a particular mode is suitable and the total number of subcarriers selected as statistical objects is less than or equal to the specified threshold value of the ratio, a decision is made that another subcarrier is suitable for use mode, otherwise it is decided that this mode is suitable for subcarrier use. Or, the ratio of the number of sub-carriers for which the spatial diversity mode is suitable is calculated to the number of sub-carriers for which the spatial multiplex mode is suitable, this ratio is compared with a predetermined threshold value for the ratio to decide on the MIMO mode suitable for use in the receiver; moreover, these methods are similar to the method described above with slight differences regarding implementation details, and thus, they can be carried out by analogy with the above procedures. The number of subcarriers for which two different modes are suitable can be compared directly, after which a decision can be made that the mode suitable for the subcarrier should be the mode corresponding to the larger number of subcarriers; if both quantities are the same, a decision is made that either mode is suitable, or that the current mode should be continued, in which case a decision can also be made using a ratio, namely a threshold value of the ratio of 50% (if this attitude is used to make a decision, then the threshold is 1).

For example, when the number of subcarriers for which the spatial multiplexing mode is suitable is calculated, then if the ratio of the number of subcarriers to the total number of subcarriers selected as statistical objects is greater than or equal to a predetermined threshold value of the ratio, it is decided that the mode is suitable for using subcarriers spatial multiplexing. Of course, the number of subcarriers for which the spatial diversity mode is also suitable can be calculated, and this process can be performed similarly.

Figure 2 shows the specific steps for implementing the above example, including:

determination of the positions of all or part of the subcarriers of the receiver;

measuring the channel coefficient corresponding to each receiver and denoted as h ₁₁ , h ₂₁ , ..., h _n1 , h ₁₂ , h ₂₂ , ..., h _n2 , ..., h _1m , ..., h _nm , where m is the number of transmitter antennas, an - the number of receiving antennas of the receiver; the definition of the channel matrix, consisting of channel coefficients corresponding to the receiver, as follows:

, запись H=H^HH и определение максимального значения λ_max и минимального значения λ_min сингулярных значений или собственных значений Н. Значение числа обусловленности канальной матрицы определяется с использованием λ_max и λ_min, и число обусловленности применяется для принятия решения о режиме MIMO, подходящего для использования поднесущей. $$H=\left[\begin{array}{cccc}{h}_{\mathrm{one}\mathrm{one}}& h_{\mathrm{one}2}& ...& h_{\mathrm{one}m}\\ ⋮& ⋮& ⋮& ⋮\\ h_{n\mathrm{one}}& {\mathrm{<figure-callout\; id="2"\; label="h\; n"\; filenames="00000026.png"\; state="\{\{state\}\}">h\; </figure-callout>}}_n& ...& h_{nm}\end{array}\right]$$

, writing H = H ^H H and determining the maximum value of λ _max and the minimum value of λ _{min of} singular values or eigenvalues of N. The value of the condition number of the channel matrix is determined using λ _max and λ _min , and the condition number is used to decide on the MIMO mode, suitable for use subcarrier.

The threshold values of two types are predetermined in advance, that is, the threshold value K _c for the subcarrier and the threshold value T _{r of the} ratio, it is assumed that the condition number of the channel matrix H _i corresponding to the subcarrier i obtained by calculation is equal to K _i .

K _i and the threshold value K _{c are} compared, and a decision is made whether the spatial multiplexing mode or the spatial diversity mode is suitable for using subcarrier i; if the spatial multiplexing mode is suitable for the subcarrier, then 1 is added to the MIMO_SM value, otherwise 1 is added to the MIMO_STC value.

, то для использования подходит режим пространственного мультиплексирования, например, предположим, что используются две приемные и две передающие антенны и сингулярное значение или собственное значение Н вычисляется как $${\lambda }_1^i$$

, $${\lambda }_2^i$$

, то, если число обусловленности определяется какIf the definitions for the condition number differ, then a decision may be made that if K _i <K _c , then the spatial diversity mode is suitable for use, or it may be decided that if $$K_i^{\text{'}\text{'}}>K_c$$

, then the spatial multiplexing mode is suitable for use, for example, suppose that two receive and two transmit antennas are used and a singular value or the eigenvalue H is calculated as $${\lambda }_{\mathrm{one}}^i$$

, $${\lambda }_2^i$$

, then if the condition number is defined as

, то принимается решение о том, что для использования поднесущей подходит режим пространственного мультиплексирования, если K_i<K_c, в противном случае принимается решение о том, что для использования поднесущей подходит режим пространственного разнесения; если число обусловленности определяется как $$K_i=\frac{min({\lambda }_1^i-{\lambda }_2^i)}{max({\lambda }_1^i-{\lambda }_2^i)}$$

или $$K_i={\lambda }_1^i\times {\lambda }_2^i$$

, предполагается, что для использования поднесущей подходит режим пространственного мультиплексирования, если K_i>K_c, в противном случае принимается решение о том, что для использования поднесущей подходит режим пространственного разнесения. Если K_i=K_c, может быть принято решение о том, что для использования поднесущей подходит режим пространственного разнесения или режим пространственного мультиплексирования. $$K_i=\frac{\left|{\lambda }_{\mathrm{one}}^i-{\lambda }_2^i\right|}{max({\lambda }_{\mathrm{one}}^i-{\lambda }_2^i)}$$

, then it is decided that the spatial multiplexing mode is suitable for using the subcarrier if K _i <K _c , otherwise it is decided that the spatial diversity mode is suitable for using the subcarrier; if the condition number is defined as $$K_i=\frac{min({\lambda }_{\mathrm{one}}^i-{\lambda }_2^i)}{max({\lambda }_{\mathrm{one}}^i-{\lambda }_2^i)}$$

or $$K_i={\lambda }_{\mathrm{one}}^i\times {\lambda }_2^i$$

, it is assumed that the spatial multiplexing mode is suitable for using the subcarrier if K _i > K _c , otherwise a decision is made that the spatial diversity mode is suitable for using the subcarrier. If K _i = K _c , a decision may be made that the spatial diversity mode or spatial multiplexing mode is suitable for using the subcarrier.

If a decision is made for all subcarriers selected as statistical objects, then the ratio Pr of subcarriers suitable for use in the spatial multiplexing mode and the subcarriers selected as statistical objects is calculated, i.e., the MIMO_SM value is divided by the sum of MIMO_SM and MIMO_STC, and the resulting quotient denoted as Pr; if Pr≥T _r , then the spatial multiplexing mode is suitable for use in the receiver; otherwise, the spatial diversity mode is suitable for use in the receiver (this process is shown in FIG. 2).

(A3) Decision making according to condition number and spectral efficiency. In this mode, several cases are also possible.

The initial steps in each of these cases coincide with the steps taken when the decision is made according to the condition number, i.e., the ratio Pr of the subcarriers suitable for use in the spatial multiplexing mode and all subcarriers selected as statistical objects is calculated first. .

(A3.1) Decide whether the diversity mode is suitable for use in the receiver if Pr <T _r ; otherwise, further applying the spectral efficiency based method to decide on a suitable MIMO mode to use. If Pr = T _r , continue the decision-making process or decide which spatial diversity mode is appropriate for use.

(A3.2) Decide that a spatial multiplexing mode is suitable for use in the receiver if Pr> T _r ; otherwise, further applying the spectral efficiency based method to decide on a suitable MIMO mode to use. If Pr = T _r , continue the decision-making process or decide which spatial multiplexing mode is appropriate for use.

(A3.3) Setting the interval of relations [T _r1 , T _r2 ], with 0≤T _r1 ≤T _r2 ≤1.

If Pr≤T _r1 , a decision is made that the diversity mode is suitable for use in the receiver; if Pr> T _r2 , a decision is made that the spatial multiplexing mode is suitable for use in the receiver; if T _R1 <Pr <T _r2 , then the decision on the suitable MIMO mode is made in accordance with spectral efficiency (in specific applications, the decision can also be made in accordance with other channel information). If Pr = T _r1 and Pr = T _r2 , the decision process can continue, or a decision can be made directly on whether the diversity / spatial multiplexing mode is suitable for use.

In this case, the decision in accordance with spectral efficiency is made exactly as described in paragraph (A1).

In practical applications, the ratio of subcarriers suitable for use in the spatial diversity mode can also be calculated with respect to all subcarriers, and a decision on the MIMO mode suitable for use by the receiver is made by comparing this ratio with a predetermined threshold value; either the ratio of the number of subcarriers suitable for use in the spatial diversity mode can be calculated to the number of subcarriers suitable for use in the spatial multiplexing mode, and the MIMO mode suitable for use by the receiver is determined by comparing this relationship with a predetermined threshold value; moreover, the implementation concept of these methods coincides with the concept of the method described above, with the exception of some implementation details, as a result of which these methods can be implemented by analogy with the algorithm described above.

(A4) Decision making in accordance with the signal-to-noise ratio

Specifies the threshold interval for the signal-to-noise ratio group, with CINR1≤CINR2.

It is assumed that a specific receiver calculates at a certain point the signal-to-noise ratio CINR in the MIMO mode currently in use.

Decide that a diversity mode is suitable for use if CINR <CINR1.

Deciding that the spatial multiplexing mode is suitable for use if CINR> CINR2.

Deciding that the current MIMO mode is suitable for use, that is, keeping the current MIMO mode unchanged if CINR1≤CINR≤CINR2.

At this point, for a receiver using the spatial diversity mode at the current time, only the threshold value CINR2 is applied, which means that the spatial multiplexing mode is used if the CINR is greater than CINR2, otherwise the spatial diversity mode is used. For a receiver that currently uses the spatial multiplexing mode, only the threshold value CINR1 is applied, which means that the spatial multiplexing mode is used if CINR is greater than CINR1, otherwise the spatial diversity mode is used.

The threshold intervals of two groups of signal-to-noise ratios can also be set: for a receiver using the spatial diversity mode at the current time, the threshold interval is set as [STC_TH _CINR 1, STC_TH _CINR 2]; for a receiver that is currently using spatial multiplexing mode, the threshold interval is set to [SM_TH _CINR 1, SM_TH _CINR 2]. In this case, STC_TH _CINR 1≤STC_TH _CINR 2, SM_TH _CINR 1≤SM_TH _CINR 2 and SM_TH _CINR 1≤STC_TH _CINR 2.

If two threshold intervals are used, [STC_TH _CINR 1, STC_TH _CINR 2] and [SM_TH _CINR 1, SM_TH _CINR 2], the processing is performed as in the case when one interval is used, the only difference is that STC_TH _CINR 1 is used instead of CINR1, and STC_TH _CINR 2 is used instead of CINR2 for a receiver currently using the spatial diversity mode; and SM_TH _CINR 1 is used instead of CINR1, and SM_TH _CINR 2 is used instead of CINR2 for a receiver that is currently using spatial multiplexing mode. This process is shown in FIG. 3, in which threshold 1 represents the above CINR1 / STC_TH _CINR 1 / SM_TH _CINR 1, and threshold 2 represents the above CINR2 / STC_TH _CINR 2 / SM_TH _CINR 2.

(A5) Decision making in accordance with the signal-to-noise ratio and spectral efficiency

If CINR1≤CINR≤CINR2 (if threshold intervals of two groups of signal-to-noise ratios are specified, then SM_TH _CINR 1≤CINR≤SM_TH _CINR 2 for a receiver that is currently using spatial multiplexing mode, or STC_TH _CINR 1≤CINR≤STC_TH _CINR 2 for a receiver currently using a spatial diversity mode), deciding on a suitable MIMO mode for use in accordance with spectral efficiency, as described in (A1).

(A6) Decision making according to signal-to-noise ratio and condition number

If CINR1≤CINR≤CINR2 (if threshold intervals of two signal-to-noise ratio groups are specified, then SM_TH _CINR 1≤CINR≤SM_TH _SINR 2 for a receiver that is currently using spatial multiplexing mode, or STC_TH _CINR 1≤CINR≤STC_TH _CINR 2 for a receiver currently using a spatial diversity mode), deciding on a MIMO mode suitable for use in accordance with the condition number as described in (A2).

(A7) Deciding according to modulation and coding values

Set the interval [DIUC1, DIUC2] for a group of modulation and coding values, with DIUC1≤DIUC2.

Assume that at a specific point in time, a specific receiver calculates a CINR signal-to-noise ratio in the MIMO mode used at the current point in time; comparing the CINR with the threshold value of entering the modulation and coding mode to determine a modulation and coding mode suitable for use by the receiver, and recording the value corresponding to the modulation and coding mode as DIUC.

Use of spatial diversity mode if DIUC <DIUC1; using spatial multiplexing mode if DIUC> DIUC2.

Deciding that the current MIMO mode is suitable for use, that is, keeping the current MIMO mode unchanged if DIUC1≤DIUC≤DIUC2.

At this point, for the receiver using the spatial diversity mode at the current time, only the DIUC2 threshold value is applied, which means that the spatial multiplexing mode is used if the DIUC is greater than DIUC2, otherwise the spatial diversity mode is used. For a receiver currently using the spatial multiplexing mode, only the threshold value DIUC1 is applied, which means that the spatial multiplexing mode is used if the DIUC is greater than DIUC1, otherwise the spatial diversity mode is used.

Threshold intervals of two groups of modulation and coding values can also be set: for a receiver using the spatial diversity mode at the current time, the threshold interval is set as [STC_TH _DIUC 1, STC_TH _DIUC 2]; for a receiver that is currently using spatial multiplexing mode, the threshold interval is set to [SM_TH _DIUC 1, SM_TH _DIUC 2]. In this case, STC_TH _DIUC 1≤STC_TH _DIUC 2, SM_TH _DIUC 1≤SM_TH _DIUC 2 and SM_TH _DIUC 1≤STC_TH _DIUC 2.

If two threshold intervals are used, [STC_TH _DIUC 1, STC_TH _DIUC 2] and [SM_TH _DIUC 1, SM_TH _DIUC 2], the processing is performed as in the case when one interval is used, the only difference is that STC_TH _DIUC 1 is used instead of DIUC1, and STC_TH _DIUC 2 is used instead of DIUC2 for a receiver currently operating in spatial diversity mode; and SM_TH _DIUC 1 is used instead of DIUC1, and SM_TH _DIUC 2 is used instead of DIUC2 for a receiver currently operating in spatial multiplexing mode. This process is shown in FIG. 3, in which threshold 1 represents the above DIUC1 / STC_TH _DIUC 1 / SM_TH _DIUC 1, and threshold 2 represents the above DIUC2 / STC_TH _DIUC 2 / SM_TH _DIUC 2.

(A8) Decision making in accordance with modulation and coding value and spectral efficiency

If DIUC1≤DIUC≤DIUC2 (if the threshold intervals of two signal-to-noise ratio groups are specified, then SM_TH _DIUC 1≤CINR≤SM_TH _DIUC 2 for the receiver currently operating in spatial multiplexing mode, or STC_TH _DIUC 1≤CINR≤STC_TH _DIUC 2 for a receiver currently operating in spatial diversity mode), deciding on a suitable MIMO mode for use in accordance with spectral efficiency in the manner described in clause (A1).

(A9) Decision making in accordance with the value of modulation and coding and the number of conditionality

If DIUC1≤DIUC≤DIUC2 (if the threshold intervals of two signal-to-noise ratio groups are specified, then SM_TH _DIUC 1≤CINR≤SM_TH _DIUC 2 for the receiver currently operating in spatial multiplexing mode, or STC_TH _DIUC 1≤CINR≤STC_TH _DIUC 2 for a receiver currently operating in spatial diversity mode), deciding on a suitable MIMO mode for use according to the condition number in the manner described in (A2).

The method may also include the following steps:

determining a modulation and coding mode in the used MIMO mode in accordance with the signal-to-noise ratio, performing by the transmitter an encoding according to the determined modulation and coding mode, and performing by the receiver a decoding according to the determined modulation and coding mode.

The modulation and coding mode can be determined by the transmitter, after which the receiver is informed about a certain modulation and coding mode, or this mode can be determined by the receiver, after which the transmitter is informed about a certain modulation and coding mode.

Moreover, the method of setting the modulation and coding mode may include at least the following steps:

(B1) Direct tuning using signal to noise ratio

If the signal-to-noise ratio can be determined in both MIMO modes (by calculating or transmitting the feedback signal), or the signal-to-noise ratio can be determined only in the MIMO mode currently used (by calculating or transmitting the feedback signal), and when this does not switch the MIMO modes, the signal-to-noise ratio in the MIMO mode used at the current time is compared with the threshold value of entering the modulation and coding mode to determine the modulation mode and is encoded MIMO mode. For example, the signal-to-noise ratio in both MIMO modes can be obtained by calculation performed at the receiver, and the modulation and coding mode in the corresponding MIMO mode can be determined based on the signal-to-noise ratio. If the spatial diversity mode is used, it is only necessary to return to the transmitter a value corresponding to the modulation and coding mode in the spatial diversity mode; if the spatial multiplexing mode is used, it is only necessary to return to the transmitter a value corresponding to the modulation and coding mode in the spatial multiplexing mode, after which the transmitter performs coding in accordance with the determined modulation and coding mode, information about which was transmitted to it via the feedback channel.

(B2) If only the signal-to-noise ratio V_CINR value can be determined in the current MIMO mode (by calculating or transmitting the feedback signal), the following operations are performed for the case when the MIMO mode is switched:

setting the value D_CINR of the difference between the signal-to-noise ratio in the spatial diversity mode and the signal-to-noise ratio in the spatial multiplexing mode under the same conditions, and if the signal-to-noise ratio in the MIMO mode used at the current time is V_CINR, and the value corresponding to the mode Since the modulation and coding obtained from the lookup table based on V_CINR is equal to V_DIUC, then there are two ways to determine the modulation and coding mode in another MIMO mode.

(B21) Determining a modulation and coding mode using a predicted signal-to-noise ratio

For a receiver using the spatial diversity mode, it can be approximately predicted that the signal-to-noise ratio of this receiver in spatial multiplexing mode is calculated as SM_CINR = V_CINR-D_CINR, after which the SM_CINR values are compared with the threshold value for entering the modulation and coding mode to determine the modulation mode and encoding the receiver in spatial multiplexing mode.

An approximate prediction can be made for a receiver using the spatial multiplexing mode that the signal-to-noise ratio of this receiver in the spatial diversity mode is calculated as STC_CINR = V_CINR-D_CINR, after which the values of STC_CINR are compared with the threshold value for entering the modulation and coding mode for determination of the modulation mode and coding of the receiver in the spatial diversity mode.

(B22) Direct prediction using the value of the modulation mode and coding in the current mode

Setting the value D of the difference between the values corresponding to the modulation and coding mode in the spatial diversity mode and in the spatial multiplexing mode, wherein D is a positive integer greater than zero.

If the receiver uses the spatial diversity mode, directly predicting that a value corresponding to the modulation and coding mode in the spatial multiplexing mode is calculated as follows: SM_DIUC = V_DIUC-D.

If the receiver uses the spatial multiplexing mode, directly predicting that the value corresponding to the modulation and coding mode in the spatial diversity mode is calculated as follows: STC_DIUC = V_DIUC + D.

It is obvious that in case (B2) it is possible to set the difference between the signal-to-noise ratios in the spatial multiplexing mode and in the spatial diversity mode (or the difference between the values corresponding to the modulation and coding modes), in which case the method can be implemented by analogy with by the aforementioned method, whereby such a method is not described.

There are three ways to implement the data transfer procedure using the corresponding MIMO mode according to the decision:

(C1) A first implementation method is shown in FIG. 4 (a), which shows the setting of a fixed switching period T. In this case, T is a positive integer greater than zero, the unit of measurement of which is the frame, and the moment of decision-making is predefined as the moment when the total number of transmitted / received frames is an integer multiple of T; after deciding on the MIMO mode to be used, data is transferred between the transmitter and receiver using this MIMO mode during the next switching period. For example, if the decision is made in the nT frame that the diversity mode is suitable for use in the receiver as the MIMO mode, as described in paragraph (C1), then the receiver uses the spatial diversity mode to receive data in nT + 1, nT frames +2, ... (n + 1) T. In the (n + 1) T frame, the system makes another decision about the MIMO mode. In this case, n is a positive integer.

(C2) A second implementation method is shown in FIG. 4 (b), which shows the setting of a fixed switching period T and a threshold value TH. In this case, T is a positive integer greater than zero, the unit of measurement of which is the frame. In each switching period, m decision points are set, i.e. m mode decisions are made without switching the MIMO mode, and the MIMO mode switching is performed only at the end of the switching period, where m is a positive integer and m≤T. The number of STC_NUM cases when the spatial diversity mode is suitable for use, and the number of SM_NUM cases when the spatial multiplexing mode is suitable for use, within m decision points during the switching period, are calculated at the end of each switching period; if the ratio of SM_NUM to m is greater than the specified TH threshold value, data between the transmitter and the receiver in the next switching period is transmitted using the spatial multiplexing mode; otherwise, data in the next switching period between the transmitter and receiver is transmitted using the spatial diversity mode (in addition, indicate that in case of equality between the ratio and the VT, the current MIMO mode will still be used, or the spatial multiplexed mode and I). For example, if it is determined in the nT frame that the spatial diversity mode is used in the next switching period, the receiver will use the spatial diversity mode in all frames nT + 1, nT + 2, ... (n + 1) T and make m decisions about the mode, and also count the number of SM_NUM cases when the spatial multiplexing mode is suitable for use. If the ratio of SM_NUM to m is greater than the specified TH threshold value, the receiver uses the spatial multiplexing mode in T frames of the next period, that is, the spatial multiplexing mode is used in all frames (n + 1) T + 1, (n + 1) T + 2, ... (n + 2) T, otherwise the receiver uses the spatial diversity mode, makes m decisions about the mode and calculates for the next period in frames (n + 1) T + 1, (n + 1) T + 2, ... (n +2) T. In practical applications, the decision on the MIMO mode used in the next switching period can also be made by comparing the ratio of STC_NUM to m or the ratio of SM_NUM to STC_NUM with a threshold value, and a specific process in this case can be performed similarly to that described. SM_NUM and STC_NUM can also be compared directly, while the spatial multiplexing mode is used if the SM_NUM value is greater, otherwise the spatial diversity mode is used, and if the SM_NUM and STCJMUM values are equal, either of the two modes or the current mode can be used; in this case, the decision can also be made using the relation SM_NUM (or STC_NUM) to m, that is, if the TH is 0.5 and the decision is made using the relation SMJMUM to STC_NUM, then the threshold value is 1.

Setting a threshold value can eliminate the problem associated with the large amount of system overhead caused by frequent switching.

(C3) FIG. 4 (c) shows a third implementation method, in accordance with which a fixed switching period T is not set, but instead a threshold value TH is set. The method is implemented as follows.

(a) For a receiver using the spatial diversity mode at the current time, a decision about the mode is always made, for example, a decision is made as soon as every decision moment comes, but the MIMO mode switch is not performed, and the decision moment can be set in advance at as the number of frames or time interval. The number of SM_NUM cases is calculated when a decision is made that the spatial multiplexing mode is suitable for use; if the ratio of SM_NUM to the total number of decision points is greater than or equal to VT, the data between the transmitter and receiver are transmitted using the spatial multiplexing mode, then step (b) is performed.

(b) For a receiver that is currently operating in spatial multiplexing mode, a decision is always made about the mode, for example, a decision is made as soon as every decision moment arrives, but the MIMO mode switch is not performed, the decision moment can be set in advance at as the number of frames or time interval. The number of STC_MUM cases is calculated when it is decided that the spatial diversity mode is suitable for use; if the ratio of STC_MUM to the total number of decision points is greater than or equal to VT, the data between the transmitter and receiver are transmitted using the spatial diversity mode, then step (a) is performed.

The present invention also provides a system for adaptive multi-input multi-output (MIMO) downlink mode switching, comprising: a transmitter and at least one receiver; wherein the transmitter may be a base station, and the receiver may be a mobile phone, laptop computer, data card, personal digital assistant (PDA) and the like, or a base station or a relay station; moreover, each receiver contains at least two receiving antennas, and each transmitter contains at least two transmitting antennas; each receiver is used to obtain information about its channel in accordance with the data received by it.

Each transmitter at least contains:

a modulation and coding unit for channels used for modulating and coding signals;

a symbol conversion module used to perform symbol conversion for signals output by a channel modulation and coding module;

a switching module used to transmit data from the output of the symbol conversion module to a data transmission module in a MIMO mode selected by the mode decision module;

a spatial multiplexing mode data transmission unit used to transmit data after performing spatial data multiplexing; and

a spatial diversity data transmission module used to transmit data after performing spatial data diversity;

however, the transmitter or receiver also contain at least:

a mode decision module used to make decisions at certain times that the MIMO mode suitable for use in the receiver is a spatial multiplex mode or a spatial diversity mode according to channel information, and to select to use the corresponding MIMO mode according to the decision, as well as to inform the switching module and the receiver about the selected MIMO mode; wherein the channel information includes one or more of the following: signal-to-noise ratio, modulation and coding mode, and the condition number of the channel matrix;

if the mode decision module is part of the transmitter, the receiver returns channel information to the mode decision module;

the receiver receives data using the MIMO mode selected by the mode decision module.

Detailed information regarding the signal-to-noise ratio and the modulation and coding mode is given above in the description of the method and is not mentioned again below.

Detailed information regarding decision-making by the decision-making module on a mode is given above in paragraphs (A1) to (A9) in the description of the method and is not mentioned again below. The mode decision module can determine the occurrence of a predetermined decision moment or the end of the switching period, for example, using a timer or counter, but is not limited to, and if necessary, counting subcarriers, STC_NUM / SM_NUM values or other values, this calculation can be performed, for example , using a counter, but is not limited to the specified, and each threshold value can be stored, for example, in memory, but is not limited to the specified.

The system may also comprise a modulation and coding mode setting module used to configure the modulation and coding mode used by the modulation and channel coding module as a mode suitable for use in the receiver in accordance with the MIMO mode selected by the mode decision module. Detailed information regarding the tuning performed by the tuning module of the modulation and coding mode is given above in paragraphs (B1) and (B2) in the description of the method and is not mentioned again below.

5 shows a transmitter comprising a mode decision module and a modulation and coding mode setting module.

The system may also include: a configuration module for configuring a decision point about a MIMO mode and for configuring a switching period.

The moment when the mode decision module makes a decision and the switch module transfers the converted data stream to the data transmission module in the corresponding MIMO mode according to the decision made by the mode decision module can be determined in three ways similar to those discussed in paragraphs (C1 ) - (C3) in the description of the method, and in the future they will not be re-mentioned.

As described above, with the adaptive switching scheme implemented by the present invention, the spatial diversity and spatial multiplexing modes are used in combination with each other, whereby the system performs adaptive switching between the spatial diversity mode and the spatial multiplexing mode, wherein the circuit corresponding to the present the invention, allows to increase the data transfer rate, maximize the use of a limited bandwidth system scan and, thus, significantly increase system throughput.

Below, the present invention is described with reference to four application examples.

First application example

It is assumed that at a certain point in time there are n receivers, designated as "User 1", "User 2", ..., "User n". Moreover, a specific receiver from these receivers is "User X", which calculates the return signal-to-noise ratio CINR in the current mode in accordance with the received information about the frequency of the pilot signal, etc. and returns the CINR value back to the transmitter through a specific IE (for example, via a fast feedback channel, etc.). The transmitter compares the received CINR value with the threshold value of entering the modulation and coding mode to select a modulation and coding mode and determines a V_DIUC value corresponding to the modulation and coding mode. Upon the occurrence of the switching period, the transmitter adjusts the modulation and coding mode after deciding on the MIMO mode and performs switching according to the returned CINR value.

The CINR value returned by the receiver is the signal-to-noise ratio only in the current MIMO mode, in which case the signal-to-noise ratio in the other MIMO mode is unknown. In this case, the processing can be performed using the decision method using only the signal-to-noise ratio described in paragraph (A4). If the threshold value in the spatial diversity mode and the threshold value in the spatial multiplexing mode are set respectively as STC_TH2 and SM_TH1, then:

1) if the current receiver mode is the spatial diversity mode, the transmitter compares CINR with the threshold value STC_TH2, and if CINR> STC_TH2, it is decided that the spatial multiplexing mode is suitable for use in the receiver, and the value corresponding to its modulation and coding mode, defined as DIUC = V_DIUC-D using a direct prediction method, wherein D is a predetermined positive integer, or a signal ratio can be predicted first l / noise in spatial multiplexing mode, and then the value corresponding to the modulation and coding mode is obtained using the predicted signal-to-noise ratio; otherwise, a decision is made to continue using the spatial diversity mode in the receiver, and the modulation and coding mode remains unchanged.

2) if the current receiver mode is spatial multiplexing mode, the transmitter compares the CINR value with the threshold value SM_TH1, and if CINR <SM_TH1, it is decided that the spatial diversity mode is suitable for use in the receiver and the value corresponding to the modulation and coding mode in spatial diversity mode, defined as DIUC = V_DIUC + D using the direct prediction method, or the signal-to-noise ratio in spatial diversity mode is first predicted I, and then a value corresponding to the modulation mode and the coding is obtained by using this predicted signal / noise ratio; otherwise, a decision is made to continue using the spatial multiplexing mode in the receiver, and the modulation and coding mode remains unchanged.

In this case, D is a positive integer. Other receivers operate according to the same algorithm as the User X receiver. The algorithm for deciding on the MIMO mode and the direct configuration of the DIUC is shown in Fig.6.

The transmitter informs the receiver of the MIMO mode selected in step 1) or 2). The transmitter transmits data in the newly selected MIMO mode, and the receiver receives data in the same mode.

Second application example

It is assumed that there are n receivers designated as "User 1", "User 2", ... "User n", each of which is equipped with two receive antennas, and the transmitter also contains only two transmit antennas. In this case, the receivers make a decision about the MIMO mode and return information about the selected MIMO mode suitable for use in the transmitter, after which the transmitter adjusts the data transmission mode in accordance with the returned MIMO mode information. The transmitter decides on the MIMO mode using the signal-to-noise ratio and spectral efficiency in the manner described in (A5). The specific process is as follows.

In this case, only one threshold value of the signal-to-noise ratio interval is used. The threshold value of the signal-to-noise ratio interval is set as a range [CINR1, CINR2]. The User X receiver calculates the return signal-to-noise ratio CINR in the mode it is currently using, according to the received information, such as the frequency of the pilot signal. Or, regardless of which mode is currently being used — spatial diversity mode or spatial multiplexing mode — for all receivers, the CINR signal-to-noise ratio is calculated only in spatial diversity mode (or in spatial multiplexing mode).

If CINR <CINR1, the diversity mode is suitable for use in the User X receiver. If CINR> CINR2, the spatial multiplex mode is suitable for use in the User X receiver. If CINR1≤CINR≤CINR2, the decision on the MIMO mode suitable for use is hereinafter made using spectral efficiency.

A specific process for evaluating spectral efficiency is performed as follows: it computes or estimates using the frequency of the pilot signal, etc., the signal-to-noise ratio for each receiving antenna in the spatial diversity mode and in the spatial multiplexing mode are recorded as STC_CINR1, STC_CINR2, SM_CINR1, respectively and SM_CINR2. The four signal-to-noise ratios can be used to determine the corresponding values of the modulation and coding order, the coding rate and the number of coding repetitions, and then to determine the corresponding spectral efficiency, the spectral efficiency = the modulation and coding order × coding rate / number of coding repetitions. The values of the modulation and coding order, coding rate, and number of coding repetitions corresponding to STC_CINR1 are recorded as STC_M1, STC_R1, and STC_P1; values corresponding to STC_CINR2 are designated as STC_M2, STC_R2 and STC_P2; values corresponding to SM_CINR1 are denoted as SM_M1, SM_R1 and SM_P1; values corresponding to SM_CINR2 are denoted as SM_M2, SM_R2 and SM_P2. The spectral efficiency corresponding to the four signal-to-noise ratios is respectively designated as STC_Effect1, STC_Effect2, SM_Effect1 and SM_Effect2. Thus, STC_Effecti = STC_Mi × STC_Ri / STC_Pi; SM_Effecti = SM_Mi × SM_Ri / SM_Pi; where i = 1, 2. Since the data transmitted by two antennas in the spatial diversity mode are the same, the total spectral efficiency in the spatial multiplexing mode and in the spatial diversity mode are STC_Effect = 0.5 × (STC_Effect1 + STC_Effect2) and SM Effect = SM, respectively Effect1 + SM_Effect2. If the STC Effect is greater than the SM Effect, User X uses the spatial diversity mode; otherwise, it uses the spatial multiplexing mode.

A decision algorithm using CINR and spectral efficiency for the receiver "User X" in the spatial diversity mode is shown in Fig.7. Other receivers use the same processing algorithm as the User X receiver.

Since the decision is made at the receiver and the signal-to-noise ratio in both MIMO modes can be obtained by calculation, the modulation and coding mode in MIMO mode can be obtained from the lookup table using the signal-to-noise ratio in the corresponding MIMO mode. The receiver returns information about the selected MIMO mode and the modulation and coding mode in this MIMO mode to the transmitter and receives data in the selected MIMO mode. The transmitter also transmits data in MIMO mode, information about which is returned by the receiver.

Third application example

, где k, j=1, 2, соответствующая взаимосвязь показана на фиг.8.It is assumed that there are n receivers designated as "User 1", "User 2", ... "User n", each of which is equipped with two receive antennas, and the transmitter also contains two transmit antennas. In this case, the decision is made using a combination of the condition number and spectral efficiency as described in paragraph (A3). The threshold value K _{c of the} subcarriers and the threshold value T, ratios, are set. For a specific User X receiver, the channel coefficients of the various receiving and transmitting antennas corresponding to their subcarrier i are written as $$h_{k,j}^i$$

where k, j = 1, 2, the corresponding relationship is shown in Fig. 8.

и могут быть представлены как $$H_i=H_i^H{H}_i$$

. Сингулярное или собственное значение H_i вычисляется как $${\lambda }_1^i$$

, $${\lambda }_2^i$$

, а число обусловленности этой матрицы может быть определено как $$K_i=\frac{\left|{\lambda }_1^i-{\lambda }_2^i\right|}{max({\lambda }_1^i-{\lambda }_2^i)}$$

(также оно может быть определено как $$K_i^{\text{'}}=\frac{min({\lambda }_1^i-{\lambda }_2^i)}{max({\lambda }_1^i-{\lambda }_2^i)}$$

или $$K_i^{"}={\lambda }_1^i{\times }_2^i$$

. Если K_i<K_c (или $$K_i^{\text{'}}>K_c$$

, или $$K_i^{"}>K_c$$

), то предполагается, что поднесущая подходит для использования в режиме пространственного мультиплексирования. Рассчитывается соотношение Pr поднесущих, для которых K_i<K_c (или $$K_i^{\text{'}}>K_c$$

, или $$K_i^{"}>K_c$$

), и если Pr<T_r, то для использования в приемнике "Пользователь X" подходит режим пространственного разнесения. В противном случае решение далее принимается с использованием спектральной эффективности.The channel matrices corresponding to these channel coefficients of the i- ^th subcarrier are written as follows: $$H_i=\left(\begin{array}{cc}{h}_{\mathrm{one}\mathrm{one}}^i& h_{\mathrm{one}2}^{\mathrm{<figure-callout\; id="2"\; label="i\; h"\; filenames="00000026.png"\; state="\{\{state\}\}">i\; </figure-callout>}}& \\ h_{}^{}{}_{2\mathrm{one}}^{\mathrm{<figure-callout\; id="2"\; label="i\; h"\; filenames="00000026.png"\; state="\{\{state\}\}">i\; </figure-callout>}}& h_{}^{}{}_{22}^i\end{array}\right)$$

and can be represented as $$H_i=H_i^H{H}_i$$

. A singular or eigenvalue H _{i is} calculated as $${\lambda }_{\mathrm{one}}^i$$

, $${\lambda }_2^i$$

, and the condition number of this matrix can be defined as $$K_i=\frac{\left|{\lambda }_{\mathrm{one}}^i-{\lambda }_2^i\right|}{max({\lambda }_{\mathrm{one}}^i-{\lambda }_2^i)}$$

(also it can be defined as $$K_i^{\text{'}\text{'}}=\frac{min({\lambda }_{\mathrm{one}}^i-{\lambda }_2^i)}{max({\lambda }_{\mathrm{one}}^i-{\lambda }_2^i)}$$

or $$K_i^{"}={\lambda }_{\mathrm{one}}^i{\times }_2^i$$

. If K _i <K _c (or $$K_i^{\text{'}\text{'}}>K_c$$

, or $$K_i^{"}>K_c$$

), it is assumed that the subcarrier is suitable for use in spatial multiplexing mode. The ratio of Pr subcarriers for which K _i <K _c (or $$K_i^{\text{'}\text{'}}>K_c$$

, or $$K_i^{"}>K_c$$

), and if Pr <T _r , then the diversity mode is suitable for use in the User X receiver. Otherwise, the decision is then made using spectral efficiency.

A specific process for evaluating spectral efficiency is performed as follows: it is calculated or estimated using the frequency of the pilot signal, etc. the signal-to-noise ratios for each receiving antenna in the spatial diversity mode and in the spatial multiplexing mode are recorded as STC_CINR1, STC_CINR2, SM_CINR1 and SM_CINR2, respectively. The four signal-to-noise ratios can be used to determine the corresponding modulation and coding order, coding rate and number of coding repetitions, and then to determine the corresponding spectral efficiency. The values of the modulation and coding order, coding rate, and number of coding repetitions corresponding to STC_CINRi are recorded as STC_Mi, STC_Ri and STC_Pi; values corresponding to SM_CINRi are denoted as SM_Mi, SM_Ri and SM_Pi; while i = 1, 2. The spectral efficiency corresponding to the four signal-to-noise ratios is respectively written as STC_Effect1, STC_Effect2, SM_Effect1 and SM_Effect2. Thus, STC_Effecti = STC_Mi × STC_Ri / STC_Pi; SM_Effecti = SM_Mi × SM_Ri / SM_Pi; where i = 1, 2. Since the data transmitted by two antennas in the spatial diversity mode are the same, the total spectral efficiency in the spatial multiplexing mode and in the spatial diversity mode are STC_Effect = 0.5 × (STC_Effect1 + STC_Effect2) and SM_Effect = SM_Effect1 +, respectively SM_Effect2. If STC_Effect is greater than SM_Effect, then the User X receiver uses the spatial diversity mode; otherwise, it uses the spatial multiplexing mode.

The decision process for other receivers is the same as for the User X receiver, and the complete process algorithm is shown in FIG. 9.

Fourth application example

It is assumed that at a certain point in time there are n receivers, designated as "User 1", "User 2", ..., "User n". They make decisions only on the basis of spectral efficiency. The decision is made based on spectral efficiency over the entire switching period, and the number of SM_NUM cases where the spatial multiplexing mode is suitable for use and the number of STC_NUM cases when the spatial diversity mode is suitable for use are calculated. The values of the initial frames for both SM_NUM and STC_NUM in each switching period are equal to zero. For a specific User X receiver, the total spectral efficiency of User X is calculated in two MIMO modes; if the spectral efficiency in the spatial diversity mode is greater than the spectral efficiency in the spatial multiplexing mode, then the value of STC_NUM increases by one, otherwise the value of SM_NUM increases by one. If at the end of the switching period STC_NUM> SM_NUM, then the spatial diversity mode is used, otherwise the spatial multiplexing mode is used. Then, at the time of the next switching and decision period, the counters STC_NUM and SM_NUM are reset. This whole process is shown in FIG. 10.

The method for calculating the spectral efficiency is similar to the method described in the second application example, that is, spectral efficiency = modulation and coding order × coding rate / number of coding repetitions.

Other receivers make the decision in the same way as the User X receiver.

Of course, many other examples of the use of the present invention can be given, and a person skilled in the art can make various corresponding changes and transformations as described in the present invention without changing the essence of the present invention, however, such changes and transformations will not fall outside the scope of the present invention, defined by the attached claims.

Industrial application

The method and system for adaptive switching modes with multiple inputs and multiple outputs (MIMO) in the downlink allows adaptive switching between modes of spatial diversity and spatial multiplexing in such a way as to achieve effective sharing of these modes and, therefore, increase the reliability of communication lines and increase system throughput, as well as solve the problem that limited bandwidth cannot be used be fully used if spatial diversity and spatial multiplexing technologies are used separately.

Claims (42)

1. The method of adaptive switching mode with multiple inputs and multiple outputs (MIMO) in the downlink used in a wireless communication system that includes a transmitter and a receiver, the method includes the following steps:
when the decision is made, the wireless communication system, in accordance with the channel information, decides that the MIMO mode suitable for use in the receiver is a spatial multiplex mode or a spatial diversity mode; data transmission between the transmitter and the receiver in the corresponding MIMO mode according to the decision;
wherein the channel information includes one or more of the following: signal-to-noise ratio, modulation and coding mode, and the condition number of the channel matrix; and
the step of making the wireless communication system in accordance with the channel information of the decision about the MIMO mode suitable for use in the receiver includes:
returning channel information from the receiver to the transmitter, the transmitter deciding in accordance with the channel information returned by the receiver, the MIMO mode suitable for use in the receiver, and informing the receiver of the selected MIMO mode after selecting the MIMO mode to be used in accordance with decision taken; or
the receiver making, in accordance with the received channel information, a decision on the MIMO mode suitable for use in the receiver, and informing the transmitter after selecting the MIMO mode of the selected MIMO mode, which must be used in accordance with the decision made. 2. The method according to claim 1, characterized in that the transmitter is a base station, and the receiver is a terminal, base station or relay station. 3. The method according to claim 1 or 2, characterized in that the step of making the wireless communication system in accordance with the channel information the decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes the following Steps:
calculation by the wireless communication system of spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver. 4. The method according to claim 3, characterized in that the step of calculating the spectral efficiency by the wireless communication system in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to channel information, includes the following steps:
calculating the STC_CINR signal-to-noise ratio for each receiver antenna of the receiver in the spatial diversity mode, determining a modulation and coding mode suitable for the spatial diversity mode in accordance with the STC_CINR ratio and determining the modulation and coding order, the coding rate, and the number of coding repeats according to the mode modulation and coding; calculating the spectral efficiency for each receiving antenna by multiplying the modulation order and coding in the spatial diversity mode by the coding rate and then dividing by the number of coding repetitions and combining the spectral efficiency values of each receiving antenna to obtain the spectral efficiency of the receiver in the spatial diversity mode; and
calculating the signal-to-noise ratio SM_CINR for each receiving antenna of the receiver in the spatial multiplexing mode, determining a modulation and coding mode suitable for the spatial multiplexing mode in accordance with the SM_CINR ratio and determining the modulation and coding order, coding rate and the number of coding repetitions in the spatial multiplexing mode in accordance with the modulation and coding mode; calculating the spectral efficiency for each receiving antenna by multiplying the modulation and coding order in the spatial multiplexing mode by the coding rate and then dividing by the number of coding repetitions and combining the spectral efficiency values of each receiving antenna to obtain the spectral efficiency of the receiver in the spatial multiplexing mode. 5. The method according to claim 3, characterized in that the step of selecting a MIMO mode with greater spectral efficiency as the MIMO mode suitable for use in the receiver includes the following steps:
if the spectral efficiency value of the SM_Effect receiver in the spatial multiplexing mode is greater than the spectral efficiency value of the STC_Effect receiver in the spatial diversity mode, decide that the spatial multiplexing mode is suitable for use in the receiver, otherwise decide what is suitable for use in the receiver spatial diversity mode; and
if the SM_Effect value is equal to the STC_Effect value, decide that the spatial multiplex mode or spatial diversity mode is suitable for use in the receiver. 6. The method according to claim 1 or 2, characterized in that the step of making the wireless communication system in accordance with the channel information the decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes the following Steps:
determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver. 7. The method according to claim 6, characterized in that the step of determining the MIMO mode suitable for use on each subcarrier, according to the condition number of the channel matrix of the receiver corresponding to each subcarrier, includes the following steps:
setting a threshold value for the subcarrier;
determining a channel matrix consisting of channel coefficients corresponding to the receiver, and calculating a condition number of the channel matrix of the receiver corresponding to each subcarrier; and
comparing the condition number of the channel matrix of the receiver corresponding to each subcarrier with the corresponding threshold value for the subcarrier to determine that each subcarrier is suitable for using the spatial diversity mode or spatial multiplexing mode. 8. The method according to claim 6, characterized in that the decision step that the particular mode is a MIMO mode suitable for use in the receiver if the ratio of subcarriers suitable for use in this mode and all subcarriers selected as statistical objects, exceeds a predetermined threshold value of the ratio, includes the following steps:
setting the threshold value Tr of the ratio;
calculating the ratio Pr of the number of subcarriers suitable for use in the spatial multiplexing mode and the number of all subcarriers selected as statistical objects, and
if the Pr value is greater than or equal to the threshold value Tr of the ratio, deciding that the MIMO mode suitable for use in the receiver should be a spatial multiplexing mode; otherwise, the decision that the MIMO mode suitable for use in the receiver should be a spatial diversity mode. 9. The method according to claim 1 or 2, characterized in that the step of making the wireless communication system in accordance with the channel information the decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes the following Steps:
determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; and
if the ratio of subcarriers suitable for use in the spatial multiplexing mode to all subcarriers selected as statistical objects is less than a predetermined ratio threshold, decide that the MIMO mode suitable for use in the receiver should be a spatial diversity mode. 10. The method according to claim 9, also including:
setting the threshold value Tr of the ratio and
calculating the ratio Pr of the number of subcarriers suitable for use in the spatial multiplexing mode and the number of all subcarriers selected as statistical objects; and
in this case, if the ratio of subcarriers suitable for use in the spatial multiplexing mode becomes less than a predetermined threshold value of the ratio, this means that the Pr value is less than the Tr value. 11. The method according to claim 10, also including:
calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if the Pr value is greater than or equal to the Tr value; and deciding that the MIMO mode with greater spectral efficiency should be the MIMO mode suitable for use by the receiver. 12. The method according to claim 10, also comprising the following steps:
setting another threshold value Tr _{2 of the} ratio, with 0≤Tr≤Tr ₂ ≤1;
if Pr> Tr ₂ , deciding that the spatial multiplexing mode is suitable for use in the receiver; and
if Tr≤Pr≤Tr ₂ , calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and determining a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver. 13. The method according to claim 1 or 2, characterized in that the step of making the wireless communication system in accordance with the channel information the decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes the following Steps:
calculating the CINR signal-to-noise ratio in the MIMO mode currently used in the receiver;
if the CINR value is greater than a predetermined threshold ratio value, deciding that the spatial multiplexing mode is suitable for use; and
if the CINR value is less than a predetermined correlation threshold value, decide that the spatial diversity mode is suitable for use. 14. The method according to item 13, wherein the predetermined threshold value of the ratio is within the interval [CINR1, CINR2], and CINR1≤CINR; and if the CINR becomes greater than a predetermined ratio threshold, this means that CINR> CINR2; and if CINR becomes less than a predetermined threshold value of the ratio, this means that CINR <CINR1. 15. The method according to 14, also including:
Deciding that the current MIMO mode is suitable for use if CINR1≤CINR≤CINR2. 16. The method according to 14, also including:
calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to channel information received by the receiver if CINR1 ≤ CINR C CINR2; and deciding that the MIMO mode with greater spectral efficiency should be the MIMO mode suitable for use in the receiver. 17. The method according to 14, also including:
determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier, by selecting all or part of the subcarriers as statistical objects if CINR1≤CINR≤CINR2; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver. 18. The method according to item 13, wherein
for a receiver using the spatial diversity mode at the current time, a predetermined threshold ratio value is within the interval [STC_TH _CINR 1> STC_TH _CINR 2], wherein STC_TH _CINR 1≤STC-TH _CINR 2;
for a receiver using the spatial multiplexing mode at the current time, the predetermined threshold value of the ratio is within the interval [SM_TH _CINR 1, SM_TH _CINR 2], with SM_TH _CINR 1≤SM_TH _CINR 2; SM_TH _CINR 1≤STC_TH _CINR 2;
for a receiver using the spatial diversity mode at the current time, the CINR value exceeding the predetermined threshold value of the ratio means that CINR> STC_TH _CINR 2; reducing CINR to a value less than a predetermined threshold value of the ratio means that CINR <STC_TH _CINR 1; and
for a receiver using the spatial multiplexing mode at the current time, the CINR value exceeding the predetermined threshold value of the ratio means that CINR> SM_TH _CINR 2; reducing CINR to a value less than a predetermined threshold value of the ratio means that CINR <SM_TH _CINR 1. 19. The method of claim 18, further comprising:
for a receiver that is currently using the spatial diversity mode, deciding that a spatial diversity mode is suitable for use in this receiver if STC_TH _CINR 1≤CINR≤STC_TH _CINR 2; and
for a receiver currently using the spatial multiplexing mode, deciding that a spatial multiplexing mode is suitable for use in this receiver if SM_TH _CINR 1 ≤ _CINR S SM_TH _CINR 2. 20. The method according to p, also including:
for a receiver currently using the spatial diversity mode, calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to channel information received by the receiver if STC_TH _CINR 1≤CINR≤STC_TH _CINR 2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver; and
for a receiver using the spatial multiplexing mode at the current time, calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if SM_TH _CINR 1≤CINR≤SM_TH _CINR 2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver. 21. The method according to p, also including:
for a receiver currently using the spatial diversity mode, determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if STC_TH _CINR 1≤ CINR≤STC_TH _CINR 2; if the ratio of subcarriers suitable for use in a particular mode and all subcarriers selected as statistical objects exceeds a predetermined ratio threshold value, deciding that said mode is a MIMO mode suitable for use in a receiver; and
for a receiver currently using the spatial multiplexing mode, determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if SM_TH _CINR 1≤ CINR≤SM_TH _CINR 2; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver. 22. The method according to claim 1 or 2, characterized in that the step of making the wireless communication system in accordance with the channel information the decision that the MIMO mode suitable for use in the receiver is a spatial multiplexing mode or a spatial diversity mode includes the following Steps:
calculating the CINR signal-to-noise ratio in the MIMO mode currently used at the receiver; and determining a modulation and coding mode suitable for use at the receiver according to the CINR, wherein the value corresponding to the modulation and coding is a downlink interval usage code (DIUC);
if the DIUC value is greater than a predetermined threshold value of the ratio, deciding that the spatial multiplexing mode is suitable for use; and
if the DIUC value is less than a predetermined correlation threshold value, decide that the spatial diversity mode is suitable for use. 23. The method according to item 22, wherein the predetermined threshold value of the ratio is within the interval [DIUC1, DIUC2], and DIUC1≤DIUC2; and if the DIUC is greater than a predetermined threshold value of the ratio, then DIUC> DIUC2; and if DIUC is less than a predetermined threshold value, then DIUC <DIUC1. 24. The method according to item 23, also including:
Deciding that the current MIMO mode is suitable for use if DIUC1≤DIUC≤DIUC2. 25. The method according to item 23, also including:
calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to channel information received by the receiver if DIUC1 ≤ DIUC D DIUC2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver. 26. The method according to item 23, also including:
determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if DIUC1≤DIUC≤DIUC2; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver. 27. The method according to item 22, wherein
for a receiver using the spatial diversity mode at the current time, a predetermined threshold ratio value is within the interval [STC_TH _DIUC 1, STC_TH _DIUC 2], with SM_TH _DIUC 1≤STC_TH _DIUC 2;
for a receiver using the spatial multiplexing mode at the current time, a predetermined threshold ratio value is within the interval [SM_TH _DIUC 1, SM_TH _DIUC 2], with SM_TH _DIUC 1≤SM_TH _DIUC 2; SM_TH _DIUC 1≤STC_TH _DIUC 2;
for a receiver using the spatial diversity mode at the current time, the DIUC value exceeding the predetermined threshold value of the ratio means that DIUC> STC_TH _DIUC 2; reducing CINR to a value less than a predetermined threshold value of the ratio means that DIUC <STC_TH _DIUC 1; and
for a receiver that is currently using spatial multiplexing mode, if the DIUC value exceeds a predetermined threshold value of the ratio, it means that DIUC> SM_TH _DIUC 2; reducing CINR to a value less than a predetermined threshold value of the ratio means that DIUC <SM_TH _DIUC l. 28. The method according to item 27, also including:
for a receiver using the spatial diversity mode at the current time, deciding that a spatial diversity mode is suitable for use in this receiver if STC_TH _DIUC 1≤DIUC <STC_TH _DIUC 2; and
for the receiver using the current time of the spatial multiplexing mode, deciding what to use in this receiver is suitable spatial multiplexing mode if SM_TH _DIUC 1≤DIUC≤SM_TH _DIUC 2. 29. The method according to item 27, also including:
for a receiver currently using the spatial diversity mode, calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver if STC_TH _DIUC 1≤DIUC≤STC_TH _D1UC 2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver; and
for a receiver that currently uses the spatial multiplexing mode, calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to channel information received by the receiver if SM_TH _DIUC 1≤DIUC≤SM_TH _DIUC 2; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver. 30. The method according to item 27, also including:
for a receiver currently using the spatial diversity mode, determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if STC_TH _DIUC 1≤ DIUC≤STC_TH _DIUC 2; if the ratio of subcarriers suitable for use in a particular mode and all subcarriers selected as statistical objects exceeds a predetermined ratio threshold value, deciding that said mode is a MIMO mode suitable for use in a receiver; and
for a receiver currently using the spatial multiplexing mode, determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects if SM_TH _DIUC 1≤ DIUC≤SM_TH _DIUC 2; if the ratio of subcarriers suitable for use in a particular mode to all subcarriers selected as statistical objects exceeds a predetermined ratio threshold, decide that the specified mode is a MIMO mode suitable for use in the receiver. 31. The method according to claim 1 or 2, also including
determining a modulation and coding mode in the used MIMO mode in accordance with the signal-to-noise ratio, performing by the transmitter an encoding according to the determined modulation and coding mode, and performing by the receiver a decoding according to the determined modulation and coding mode. 32. The method according to p. 31, characterized in that if the signal-to-noise ratio can be determined in both MIMO modes or the signal-to-noise ratio can be determined only in the MIMO mode used at the current time, and there is no mode switching MIMO, the step of determining the modulation and coding mode in the MIMO mode used in accordance with the signal-to-noise ratio includes the following steps:
comparing the signal-to-noise ratio in the used MIMO mode with the threshold value of entering the modulation and coding mode and determining the modulation and coding mode in the MIMO mode. 33. The method according to p. 31, characterized in that if only the signal-to-noise ratio in the MIMO mode used at the current time can be determined and the MIMO modes are switched, the step of determining the modulation and coding mode in the MIMO mode used in accordance with the signal-to-noise ratio, contains the following steps:
setting the difference value D_CINR between the signal-to-noise ratio in the spatial diversity mode and the signal-to-noise ratio in the spatial multiplexing mode under the same conditions, comparing the signal-to-noise ratio V_CINR in the MIMO mode currently used in the receiver with the threshold value for entering the mode modulation and coding, and determining a modulation and coding mode in the MIMO mode currently used;
calculating for the receiver using the spatial diversity mode, the signal-to-noise ratio SM_CINR = V_CINR-D_CINR in the spatial multiplexing mode, comparing the SM_CINR value with a threshold value for entering the modulation and coding mode, and determining the modulation and coding mode of the receiver in the spatial multiplexing mode, and
calculating for the receiver using the spatial multiplexing mode, the signal-to-noise ratio STC_CINR = V_CINR + D_CINR in the spatial diversity mode, comparing the STC-CINR value with a threshold value for entering the modulation and coding mode, and determining the modulation and coding mode of the receiver in the spatial diversity mode. 34. The method according to p. 31, characterized in that if only the signal-to-noise ratio can be determined in the MIMO mode used at the current time, and the MIMO modes are switched, the step of determining the modulation mode and coding in the MIMO mode used in According to the signal-to-noise ratio, it includes the following steps:
setting the difference D between the values corresponding to the modulation and coding modes in the spatial diversity mode and in the spatial multiplexing mode, comparing the signal-to-noise ratio V_CINR in the MIMO mode currently used in the receiver with the threshold value for entering the modulation and coding mode, and determination of the modulation and coding mode in the MIMO mode used at the current time, the value corresponding to the modulation and coding mode is denoted by V_DIUC;
calculating the value SM_DIUC = V_DIUC-D corresponding to the modulation and coding mode of the receiver using the spatial diversity mode in the spatial multiplexing mode and
calculating a value of STC_DIUC = V_DIUC + D corresponding to a modulation and coding mode of a receiver using the spatial multiplexing mode in the spatial diversity mode. 35. The method according to claim 1 or 2, including
setting the switching period T using frames as units of measurement and
preliminary specification of the moment of decision-making as the moment at which the total number of transmitted / received frames is an integer multiple of T;
the step of transmitting data using the appropriate MIMO mode according to the decision made includes: after deciding on the MIMO mode suitable for use, data transfer between the transmitter and receiver using this MIMO mode in the next switching period. 36. The method according to claim 1 or 2, including also:
setting a switching period T using frames as units of measurement, as well as setting a threshold value of VT, and
setting m decision decision times in each switching period, where m is a positive integer and m≤T;
the step of transmitting data using the appropriate MIMO mode according to the decision made includes: counting the number of STC_NUM cases when it is advisable to use the spatial diversity mode, and the number of SM_NUM cases when it is advisable to use the spatial multiplexing mode, in m decisions made during the current switching period to the end of each switching period; and transmitting data between the transmitter and the receiver using the spatial multiplexing mode in the next switching period, if the ratio of SM_NUM to m is greater than TH, otherwise, transmitting data using the spatial diversity mode in the next switching period. 37. The method according to claim 1 or 2, characterized in that the step of transmitting data using the corresponding MIMO mode according to the decision contains the following steps:
setting the threshold value of VT;
for a receiver using the spatial diversity mode, counting the number of SM_NUM cases when it is decided that the spatial multiplexing mode is suitable for use; if the ratio of SM_NUM to the total number of decision-making cases is greater than TH, then switching to the spatial multiplexing mode for data transmission between the transmitter and receiver; and
for a receiver using the spatial multiplexing mode, counting the number of STC_NUM cases when it is decided that the spatial diversity mode is suitable for use; if the ratio of STC_NUM to the total number of decision cases is greater than TH, then switch to spatial diversity mode to transfer data between the transmitter and receiver. 38. System for adaptive mode switching with multiple inputs and multiple outputs (MIMO) in the downlink, comprising a transmitter and at least one receiver; wherein each receiver contains at least two receiving antennas, and each transmitter contains at least two transmitting antennas; each receiver is used to obtain channel information based on data received; is used to obtain channel information based on data received by the receiver; the transmitter comprises: a modulation and coding module for channels used for modulating and coding signals; and a symbol conversion module used to perform symbol conversion for signals output by the modulation and coding module;
wherein the transmitter or receiver at least comprise:
a decision module about the mode used at the time of the decision to decide that the MIMO mode suitable for use in the receiver is a spatial multiplex mode or a spatial diversity mode, in accordance with the channel information; and selecting the appropriate MIMO mode for use according to the decision made, as well as for informing the switching module and the receiver of the selected MIMO mode; wherein the channel information includes one or more of the following: signal-to-noise ratio, modulation and coding mode, and the condition number of the channel matrix;
The transmitter also contains:
a switching module used to transmit data from the output of the symbol conversion module to a data transmission module in a MIMO mode selected by the mode decision module;
a spatial multiplexing mode data transmission unit used to transmit data after performing spatial data multiplexing; and
a spatial diversity data transmission module used to transmit data after performing spatial data diversity;
in this case, the receiver receives data in the MIMO mode selected by the mode decision module. 39. The system of claim 38, wherein the transmitter is a base station, and the receiver is a terminal, base station, or relay station. 40. The system according to § 38 or 39, characterized in that the decision that the MIMO mode suitable for use in the receiver is the spatial multiplexing mode or spatial diversity mode, in accordance with the channel information, is as follows:
A) the calculation by the wireless communication system of spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver;
B) determining a MIMO mode suitable for use on each subcarrier, according to the condition number of the channel matrix of the receiver corresponding to each subcarrier, by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in a particular mode and all subcarriers selected as statistical objects exceeds a predetermined ratio threshold value, deciding that said mode is a MIMO mode suitable for use in a receiver;
C) determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in spatial multiplexing mode to all subcarriers selected as statistical objects is less than a predetermined ratio threshold, decide that the MIMO mode suitable for use in the receiver is spatial diversity mode, in Otherwise, perform one of the following two steps:
C1) if the ratio of subcarriers suitable for use in the spatial multiplexing mode is greater than another predetermined ratio threshold value, deciding that the MIMO mode suitable for use in the receiver should be the spatial multiplexing mode, otherwise, perform step C2; or
C2) calculating spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver;
D) calculating the CINR signal-to-noise ratio in the MIMO mode currently used at the receiver; if the CINR is greater than the first predetermined ratio threshold value, deciding that the spatial multiplexing mode is suitable for use; and if the CINR is less than the second predetermined threshold value of the ratio, deciding that the spatial diversity mode is suitable for use; if the CINR value is less than or equal to the first predetermined ratio threshold value and greater than or equal to the second predetermined ratio threshold value, perform one of two of the following steps:
D1) calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver; or
D2) determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier by selecting all or part of the subcarriers as statistical objects; if the ratio of subcarriers suitable for use in a particular mode and all subcarriers selected as statistical objects exceeds a predetermined ratio threshold value, deciding that said mode is a MIMO mode suitable for use in a receiver;
E) the calculation of the signal-to-noise ratio CINR in the MIMO mode currently used in the receiver; determining a modulation and coding mode suitable for use at the receiver according to CINR, wherein the value corresponding to modulation and coding is DIUC; if the DIUC is greater than the first predetermined ratio threshold value, deciding that the spatial multiplexing mode is suitable for use; and if the DIUC is less than the second predetermined threshold value of the ratio, deciding that the spatial diversity mode is suitable for use; if the DIUC value is less than or equal to the first predetermined ratio threshold value and greater than or equal to the second predetermined ratio threshold value, perform one of two of the following steps:
E1) calculating the spectral efficiency in the spatial diversity mode and in the spatial multiplexing mode, respectively, according to the channel information received by the receiver; and deciding on a MIMO mode with greater spectral efficiency as a MIMO mode suitable for use in a receiver; or
E2) determining a MIMO mode suitable for use on each subcarrier according to the condition number of the channel matrix of the receiver corresponding to each subcarrier, by selecting all or that said mode is a MIMO mode suitable for use in the receiver. 41. The system of claim 38 or 39, wherein the transmitter or receiver also comprises: a modulation and coding mode tuning module used to configure a modulation and coding mode used by the modulation and coding module of the channels as a mode suitable for use in the receiver , in accordance with the MIMO mode selected by the mode selection module in one of the following ways:
a) if the signal-to-noise ratio can be determined in both MIMO modes or the signal-to-noise ratio can only be determined in the MIMO mode used at the current moment in time, and MIMO modes are not switched, performing signal-to-noise comparison in the mode MIMO used at the current time, with a threshold value for entering the modulation and coding mode, and determining a modulation and coding mode for the MIMO mode;
b) if only the signal-to-noise ratio in the MIMO mode used at the current time can be determined, and the MIMO modes are switched, setting the difference value D_CINR between the signal-to-noise ratio in the spatial diversity mode and the signal-to-noise ratio in the spatial multiplexing mode at the same conditions, comparing the signal-to-noise ratio V_CINR in the MIMO mode currently used in the receiver with the threshold value for entering the modulation and coding mode, and determining the modulation mode and dirovaniya in MIMO mode, which is the current time; calculating the signal-to-noise ratio SM_CINR = V_CINR-D_CINR for a receiver using the spatial diversity mode in the spatial multiplexing mode, comparing the SM_CINR value with a threshold value for entering the modulation and coding mode, and determining a modulation and coding mode of the receiver in the spatial multiplexing mode; and also calculating the spatial multiplexing ratio, comparing the SM_CINR value with a threshold value for entering the modulation and coding mode, and determining a modulation and coding mode of the receiver in the spatial multiplexing mode; as well as calculating a signal-to-noise ratio STC_CINR = V_CINR + D_CINR for a receiver using the spatial multiplexing mode in the spatial diversity mode, comparing the STC_CINR value with a threshold value for entering the modulation and coding mode and determining a modulation and coding mode of the receiver in the spatial diversity mode; and
c) if only the signal-to-noise ratio can be determined in the MIMO mode currently in use, and the MIMO modes are switched, the difference D is set between the values corresponding to the modulation and coding modes in the spatial diversity mode and in the spatial multiplexing mode, comparing the ratio signal / noise V_CINR in the MIMO mode currently used in the receiver, with a threshold value for entering the modulation and coding mode and determining the modulation and coding mode in the MIMO mode, used at the current time, and the value corresponding to the modulation mode and coding is denoted by V_DIUC; calculating the value SM_DIUC = V_DIUC-D corresponding to the modulation and coding mode of the receiver using the spatial diversity mode in the spatial multiplexing mode; and calculating the value of STC_DIUC = V_DIUC + D corresponding to the modulation and coding mode of the receiver using the spatial multiplexing mode in the spatial diversity mode. 42. The system according to § 38 or 39, characterized in that the transmitter or receiver also comprises a configuration module for configuring a decision point about a MIMO mode, wherein the configuration module is also used for:
i) setting the switching period T using frames as units of measurement,
wherein the configuration module sets the decision moment at which the decision on the MIMO mode is made, as the moment when the total number of transmitted / received frames is an integer multiple of T; and the mode decision module selecting the appropriate MIMO mode for use according to the decision made, does the following: after deciding on a suitable MIMO mode for use, the mode decision module selects the MIMO mode for use;
ii) setting the switching period T using frames as units of measurement,
wherein the configuration module sets m decision decision times in each switching period, wherein m is a positive integer and m≤T; a mode decision module that selects the appropriate MIMO mode to use according to the decision made, performs the following: counts the number of STC_NUM and SM_NUM cases when the spatial diversity mode and spatial multiplex mode are suitable for use, in m decisions during the current switching period until the end of each period switching; selects a spatial multiplexing mode for use in the next switching period, if the ratio of SM_NUM to m is greater than a predetermined threshold TH, otherwise selects a spatial diversity mode for use in the next switching period; or
iii) configuring the decision point,
wherein the mode decision module selecting the appropriate MIMO mode to use according to the decision made does the following: for a receiver using the spatial diversity mode, it counts the number of SM_NUM cases when it is decided that the spatial multiplexing mode is suitable for use; if the ratio of SM_NUM to the total number of decision cases is greater than a predetermined threshold value of the VT, selects to use the spatial multiplexing mode for receiving data; for a receiver using the spatial multiplexing mode, counts the number of STC_NUM cases when it is decided that the spatial diversity mode is suitable for use; if the ratio of STC_NUM to the total number of decision-making cases is greater than the VT, selects the spatial diversity mode for use.

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