CN108347266A - Receiving device and receiving method for determining modulation and coding scheme based on channel capacity - Google Patents

Abstract

A receiving device and a receiving method for determining a modulation and coding scheme based on channel capacity, the receiving device comprising a channel estimation unit, for generating a plurality of channel estimates based on a plurality of reference signals; an eigenvalue calculation unit, coupled to the channel estimation unit, for generating at least one eigenvalue corresponding to the plurality of channel estimates based on the plurality of channel estimates; a channel compensation unit, coupled to the eigenvalue calculation unit, for generating a correlation correction value for compensating the plurality of channel estimates based on the at least one eigenvalue; a channel capacity calculation unit, coupled to the eigenvalue calculation unit and the channel compensation unit, for generating a channel capacity based on the at least one eigenvalue and the correlation correction value; and a selection unit, coupled to the channel capacity calculation unit, for determining a modulation and coding scheme based on the channel capacity.

Description

Receiving device and receiving method for determining modulation and coding scheme based on channel capacity

technical field

The present invention relates to a device and method used in a communication system, in particular to a device and method for determining modulation and coding schemes.

Background technique

In a wireless communication system, since the channel is time-varying, in order to improve the throughput of the client, the receiving end will select a better modulation and coding scheme (MCS) according to the channel condition, and the selected The modulation and coding method is reported to the transmitting end. After receiving the modulation and coding scheme from the receiving end, the transmitting end can use the received modulation and coding scheme to transmit data.

Generally, the receiving end will use Exponential Effective SINR Mapping (EESM) to select a modulation and coding scheme. However, the exponential effective SINR mapping is suitable for linear detectors, but it is difficult to apply to multiple-input multiple-output (MIMO) nonlinear detectors.

Therefore, how to select a modulation and coding scheme more accurately in the case of using a nonlinear detector has become an urgent problem to be solved.

Contents of the invention

Therefore, the present invention provides a receiving device and a receiving method, which can be applied to a receiving device with a linear detector or a nonlinear detector to determine the modulation and coding scheme, so as to solve the above problems.

The invention discloses a receiving device, which includes a channel estimation unit for receiving a plurality of reference signals, and generates a plurality of channel estimations according to the plurality of reference signals; an eigenvalue calculation unit is coupled to the channel estimation unit , used to generate at least one eigenvalue (eigenvalue) corresponding to the plurality of channel estimates according to the plurality of channel estimates; a channel compensation unit, coupled to the eigenvalue calculation unit, used to generate at least one eigenvalue according to the at least one eigenvalue, generating a correlation correction value for compensating the plurality of channel estimates; a channel capacity calculation unit coupled to the eigenvalue calculation unit and the channel compensation unit for modifying the value according to the at least one eigenvalue and the correlation, generating a channel capacity; and a selection unit coupled to the channel capacity calculation unit for determining a modulation and coding scheme (MCS) according to the channel capacity.

The present invention also discloses a receiving method for a receiving device, including receiving a plurality of reference signals, generating a plurality of channel estimates according to the plurality of reference signals; and generating the corresponding plurality of channels according to the plurality of channel estimates Estimated at least one eigenvalue (eigenvalue); according to the at least one eigenvalue, generate a correlation correction value for compensating the plurality of channel estimates; generate a channel capacity according to the at least one eigenvalue and the correlation correction value ; and according to the channel capacity, determine a modulation and coding scheme (modulation and coding scheme, MCS).

Description of drawings

FIG. 1 is a schematic diagram of a communication system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a receiving device according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a channel quality number and bit efficiency correspondence table according to an embodiment of the present invention.

Fig. 4 is a flow chart of the process of the embodiment of the present invention.

Detailed ways

FIG. 1 is a schematic diagram of a communication system 10 according to an embodiment of the present invention. The communication system 10 can be any communication system that uses an orthogonal frequency-division multiplexing (OFDM) technology (or called a discrete multi-tone modulation (DMT) technology), and briefly consists of a It consists of a transmitting end TX and a receiving end RX. In FIG. 1 , the transmitting end TX and the receiving end RX are used to illustrate the architecture of the communication system 10 . For example, the communication system 10 may be an asymmetric digital subscriber line (ADSL) system, a power line communication (PLC) system, an Ethernet over coax (EOC) system, etc. Wired communication system, or wireless local area network (wireless local area network, WLAN), digital video broadcasting (Digital Video Broadcasting, DVB) system, long-term evolution (LongTerm Evolution, LTE) system and advanced long-term evolution (LTE-advanced, LTE-A ) system and other wireless communication systems. In addition, the transmitting end TX and the receiving end RX can be set in devices such as mobile phones and notebook computers, but are not limited thereto

FIG. 2 is a schematic diagram of a receiving device 20 according to an embodiment of the present invention, which is used in the receiving end RX in FIG. 1 to determine (for example, select) a modulation and coding scheme. The receiving device 20 includes a channel estimation unit 200 , an eigenvalue calculation unit 210 , a channel compensation unit 220 , a channel capacity calculation unit 230 and a selection unit 240 . In detail, after the receiving device 20 receives the plurality of reference signals sig_ref, the channel estimation unit 200 can generate a plurality of channel estimates ch_est according to the plurality of reference signals sig_ref (for example, perform channel estimation). Wherein, the plurality of reference signals sig_ref can be known signals such as pilot signals and preambles that can be used to estimate the channel, but are not limited thereto. The eigenvalue calculation unit 210 is coupled to the channel estimation unit 200 and is configured to generate at least one eigenvalue (eigenvalue) eig_ch corresponding to the plurality of channel estimates ch_est according to the plurality of channel estimates ch_est. The channel compensation unit 220 is coupled to the eigenvalue calculation unit 210 and can generate a correlation correction value corr_comp for compensating a plurality of channel estimates ch_est according to at least one eigenvalue eig_ch. The channel capacity calculation unit 230 is coupled to the eigenvalue calculation unit 210 and the channel compensation unit 220, and can generate the channel capacity cap_est according to at least one eigenvalue eig_ch and a correlation correction value corr_comp. The selection unit 240 is coupled to the channel capacity calculation unit 230 and can determine a modulation and coding scheme (modulation and coding scheme, MCS) mcs_sel according to the channel capacity cap_est.

That is to say, as time changes, the channel will also change accordingly, and the estimated plurality of channel estimates ch_est may have a high correlation, for example, due to the correlation caused by multiple antennas. The channel capacity calculation unit 230 may use the correlation correction value corr_comp when estimating the channel capacity cap_est, so that the channel capacity cap_est reflects the negative effect caused by the correlation. Therefore, the selection unit 240 can determine the modulation and coding scheme mcs_sel suitable for the current channel condition according to the more accurate channel capacity, thereby improving the throughput of the receiving end RX. In addition, the receiving device 20 can be applied to a linear detector (linear detector) or a nonlinear detector (non-linear detector), which solves the exponential effective signal-to-noise and interference ratio (SINR) Mapping (Exponential Effective SINR Mapping, EESM) can only be applied to linear detector problems.

In one embodiment, the selection unit 240 can generate a bit efficiency (BitEfficiency) according to the channel capacity cap_est, and the selection unit 240 can determine a modulation and coding scheme according to the bit efficiency. Furthermore, the selection unit 240 may determine the modulation and coding scheme according to the bit efficiency so that a block error rate (BLER) of the receiving device 20 conforms to a predetermined block error rate (eg, 10%). In one embodiment, the eigenvalue calculation unit 210 may generate at least one eigenvalue eig_ch corresponding to the plurality of channel estimates ch_est according to Singular value decomposition (SVD). That is to say, the eigenvalue calculation unit 210 uses singular value decomposition to calculate at least one eigenvalue eig_ch, so as to reduce the complexity (ie power consumption) of calculating at least one eigenvalue eig_ch.

In one embodiment, the selection unit 240 further includes a layer processing unit 242 capable of dividing the channel capacity cap_est to generate a plurality of channel capacities corresponding to a plurality of layers. Further, the layer processing unit 242 may divide the channel capacity cap_est in the following manner: equally divide the channel capacity cap_est, or divide the channel capacity cap_est according to the multiple power levels of the multiple layers. That is to say, when the transmitting end TX uses MIMO, the data transmission will be transmitted through multiple layers, that is, the data transmission will be allocated to multiple streams, and these streams may experience different channel. In this embodiment, the layer processing unit 242 calculates these channel capacities, and then determines the corresponding modulation and coding schemes for these channel capacities (ie, layers), so as to improve throughput. There are many ways for the hierarchical processing unit 242 to divide the channel capacity cap_est. For example, the stratum processing unit 242 can divide the channel capacity cap_est equally, that is, the channel capacity allocated to each stratum is the same. This simple allocation can reduce the complexity of the receiving device 30 . In another embodiment, the layer processing unit 242 can divide the channel capacity cap_est according to the power levels of the layers. This allocation method can further improve throughput.

In one embodiment, according to at least one eigenvalue eig_ch, the channel compensation unit 220 can generate a condition number of the plurality of channels, and according to the condition number, the channel compensation unit 220 can generate a correlation correction value corr_comp. That is, the channel compensation unit 220 may obtain the correlation correction value corr_comp by using the condition number.

The following embodiments are used to illustrate how the eigenvalue calculation unit 210 determines at least one eigenvalue eig_ch according to the channel estimation ch_est. First, the eigenvalue calculation unit 210 calculates the M×M covariance matrix R _i of the channel as follows:

where H _k is the M×N (estimated) channel matrix with subcarrier number k, M is the number of antennas at the receiving end, N is the number of antennas at the transmitting end, () ^H is the conjugate transpose operation. RB _i is a measurement unit, which can be a single subcarrier, or a resource block (RB) as specified in the LTE system. Taking the case where the unit of measurement is a resource block as an example, is the number of resource blocks in the downlink (downlink, DL), and K is the number of subcarriers used in one measurement unit. Next, the eigenvalue calculation unit 210 calculates the eigenvalues of the covariance matrix R _i , for example, at least one eigenvalue eig_ch can be obtained through the singular value decomposition of formula 2:

Where U _i is an M×M unitary matrix, V _i is an M×M unitary matrix, S _i is an M×M diagonal matrix, S _i =diag(λ _{i, 0} , λ _{i, 1} ,… , λ _{i, M-1} ), λ _{i, 0} ≥ λ _{i, 1} ≥...≥ λ _{i, M-1} , where, λ _{i, m} , m=0, 1, ..., M-1 is the covariance Singular values (i.e., eigenvalues) of the matrix R _i .

According to the hierarchy used for transmission, the channel capacity calculation unit 230 uses the eigenvalues to calculate the channel capacity C _i can be divided into two cases:

The first case is single layer (Single layer): such _as long-term evolution _TM1 , TM2, TM4Rank 1 and other transmission modes _, the channel capacity calculation unit 230 can calculate the _M-1 calculates the channel capacity C _i , and its equation is as follows:

in, is the energy of the noise. In this embodiment, the channel compensation unit 220 may be omitted or disabled.

The second case is Multiple layers: such as long-term evolution TM3, TM4Rank2 and other transmission modes, the channel capacity calculation unit 230 can be based on eigenvalues λ _{i, D ,} λ _{i, 1 ,} . The correlation correction value ε _i calculates the channel capacity C _i , and its equation is as follows:

The manner of obtaining the correlation correction value ε _i will be described in detail below. The channel compensation unit 220 can first calculate the condition number k _i according to the eigenvalues λ _{i, 0} , λ _{i, 1} , ..., λ _{i, M-1} as follows:

Next, the channel compensation unit 220 calculates the correlation correction value ε _i according to the condition number k _i as follows:

Wherein, in one embodiment, the parameters can be set as follows: α _L =1, α _M =2, α _H =4, α=32.

In the case of a single layer, the selection unit 240 selects a modulation and coding scheme according to the channel capacity C _i . In the case of multiple levels, the selection unit 240 may select modulation and coding schemes (same or different) according to channel conditions of each level. The following is an example of two classes to illustrate two embodiments of allocating channel capacity:

The first embodiment: the stratum processing unit 242 equally distributes the channel capacity to the two strata. In this case, since the coding and modulation schemes of the two levels are the same, the receiving device only needs to report the modulation and coding schemes of each level. The hierarchical processing unit 242 can calculate the channel capacity as follows:

Among them, C _0,i and C _1,i are the channel capacity of the first level and the second level respectively.

Embodiment 2: The layer processing unit 242 calculates the channel capacities of the two layers respectively. In this case, the receiving device must report the modulation and coding schemes of each layer. Taking Long Term Evolution TM4Rank 2 as an example, the channel matrix is expressed as Afterwards, the level processing unit 242 can calculate the channel capacity by calculating the power level of each level as follows:

If p _0,i ≥p _1,i , the hierarchical processing unit 242 can obtain the channel capacity as follows:

in

On the contrary, if p _0,i <p _1,i , the channel capacity obtained by the hierarchical processing unit 242 is as follows:

in

After the channel capacity is obtained according to the foregoing, the selection unit 240 can determine the modulation and coding scheme accordingly. The following embodiments are used to illustrate how the selection unit 240 determines the modulation and coding scheme according to the channel capacity. The selection unit 240 first calculates the average value of the channel capacity of each stratum as follows:

Where l is the class number. Next, the selection unit 240 can use the conversion function f _c () to convert the channel capacity C _l into the bit efficiency C' _l = f _c (a, C _l ), where f _c () is the corresponding system block error rate ( For example, 10%) of the transfer function, a is a group of coefficients corresponding to single-level or multi-level. The selection unit 240 can compare C' _l with a predetermined bit efficiency y _n , n=1, 2, ..., 15, to select the channel quality number n _l corresponding to the bit efficiency as follows:

n _l = min _{n = 0, ..., 15} {C' _l -y _n | C' _l ≥ y _n } (Formula 12)

Therefore, the receiving device can transmit the channel quality number n _l to the transmitting end, so that the transmitting end can learn a better modulation and coding scheme according to the channel quality number n _l .

FIG. 3 is a schematic diagram of a channel quality number and bit efficiency correspondence table 30 according to an embodiment of the present invention. Fig. 3 illustrates the corresponding relationship among different channel quality numbers, modulation and coding schemes, modulation, code rate and bit efficiency. According to the previous description, if the channel capacity estimated by the receiving end RX is converted by the conversion function to obtain a bit efficiency of 3.8, the receiving device 20 can calculate the corresponding bit efficiency of 3.3223 according to the corresponding table 30, and return the channel quality number "11" to the transmitting end TX to notify the transmitting end TX to use the modulation and coding mode "21". In other words, the selection unit determines the modulation and coding scheme according to the bit efficiency, so that the block error rate of the receiving device 20 can meet the requirement of a predetermined block error rate (eg, 10%). Of course, when the block error rate required by the system changes, the conversion function f _c () needs to be changed accordingly. In other words, why the conversion function f _c () depends on the set block error rate requirement.

It should be noted that there are many forms of f _c (), as long as the channel capacity C _l can be properly converted into bit efficiency C' _l . The following example illustrates a method for determining the quadratic polynomial f _c (a, x)=a ₂ x ² +a ₁ x+a ₀ .

1. Select the channel quality number j, and randomly generate a fading channel for system simulation of the block error rate.

2. Calculate the signal-to-noise ratio (SNR) required for a block error rate of 10%, and input the signal-to-noise ratio into the channel capacity calculation to obtain c _j,n .

3. Repeat steps 1 and 2 for a total of N times, and calculate the average channel capacity of N fading channels as follows:

4. Repeat steps 1, 2 and 3 until the average channel capacity X _j of all channel quality numbers is obtained, j=1, 2, . . . , 15.

5. Define X=[X ₁ X ₂ ... X ₁₅ ] as the average channel capacity vector matrix of the channel quality number, and Y=[y ₁ y ₂ ...y ₁₅ ]=[0.1523 0.2344 ... 5.5547] as the bit efficiency of the channel quality number vector matrix. In one embodiment, the polynomial f _c (a, C _l ) can be obtained using least square error as follows:

J(X, Y)＝min{|Yf _c (a, X)| ² } (Formula 14)

When used in single-level cases, [a ₂ a ₁ a ₀ ]=[0.014 0.7052 - 0.0609] can be roughly obtained, and when used in multi-level cases, [a ₂ a ₁ a ₀ ]=[ 0.212 0.6407 0.0843].

The above-mentioned operation mode of the receiving device 20 can be summarized into a process 40, which is used in the receiving end RX, as shown in FIG. 4 . Process 40 includes the following steps:

Step 400: start.

Step 402: Receive a plurality of reference signals, and generate a plurality of channel estimates according to the plurality of reference signals.

Step 404: Generate at least one eigenvalue corresponding to the plurality of channels according to the plurality of channel estimates.

Step 406: Generate a correlation correction value for compensating the plurality of channels according to the at least one eigenvalue.

Step 408: Generate a channel capacity according to the at least one eigenvalue and the correlation correction value.

Step 410: Determine a modulation and coding scheme according to the channel capacity.

Step 412: end.

The process 40 is used as an example to explain the operation of the receiving device 20 , and the detailed description and changes can be referred to above, and will not be repeated here.

It should be noted that there are many ways to realize the receiving device 20 (and the channel estimation unit 200 , the feature value calculation unit 210 , the channel compensation unit 220 , the channel capacity calculation unit 230 and the selection unit 240 ). For example, the units described above may be integrated into one or more units. In addition, the receiving device 20 can be hardware (such as a circuit), software, firmware (a combination of a hardware device and computer instructions and data, and the computer instructions and data belong to read-only software on the hardware device), an electronic system, or the components of the above-mentioned devices. Combination to achieve, not limited to this.

To sum up, the present invention provides a device and method for determining (for example, selecting) a modulation and coding scheme, which can be applied to a linear detector or a nonlinear detector, and can be used to determine the most suitable channel capacity based on a more accurate channel capacity. Modulation and coding methods for channel conditions, thereby improving system throughput.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

【Symbol Description】

20 Receiver

200 channel estimation units

210 eigenvalue calculation unit

220 channel compensation unit

230 channel capacity calculation unit

240 selection units

242 Hierarchical Processing Units

30 tables

40 process

400, 402, 404, 406, 408, steps

410, 412

sig_ref reference signal

ch_est channel

eig_ch eigenvalue

corr_comp correlation correction value

cap_est channel capacity

mcs_sel modulation and coding method

TX transmitter

RX receiver.

Claims (10)

1. A receiving device, comprising:

a channel estimation unit for receiving a plurality of reference signals and generating a plurality of channel estimates according to the plurality of reference signals;

a characteristic value calculating unit, coupled to the channel estimating unit, for generating at least one characteristic value corresponding to the plurality of channel estimates according to the plurality of channel estimates;

a channel compensation unit, coupled to the eigenvalue calculation unit, for generating correlation correction values for compensating the plurality of channel estimates according to the at least one eigenvalue;

a channel capacity calculation unit, coupled to the eigenvalue calculation unit and the channel compensation unit, for generating a channel capacity according to the at least one eigenvalue and the correlation correction value; and

the selection unit is coupled to the channel capacity calculation unit and used for determining a modulation coding mode according to the channel capacity.

2. The receiving device as claimed in claim 1, wherein the selecting unit generates a bit efficiency according to the channel capacity, and the selecting unit determines the modulation coding scheme according to the bit efficiency.

3. The receiving device of claim 2, wherein the selection unit determines the modulation coding scheme based on the bit efficiency such that the bler of the receiving device meets a predetermined bler.

4. The receiving device according to claim 1, wherein the eigenvalue calculation unit generates the at least one eigenvalue corresponding to the plurality of channel estimates according to a singular value decomposition.

5. The receiving device as claimed in claim 1, wherein the selecting unit further comprises:

the hierarchy processing unit is coupled to the channel capacity calculation unit and used for dividing the channel capacity to generate a plurality of channel capacities corresponding to a plurality of hierarchies.

6. The receiving device of claim 5, wherein the hierarchical processing unit divides the channel capacity in the following manner: the channel capacity is divided equally or divided according to a plurality of power levels of the plurality of levels.

7. The receiving device of claim 1, wherein the channel compensation unit generates a condition number for the plurality of channels according to the at least one characteristic value, and the channel compensation unit generates the correlation correction value according to the condition number.

8. A receiving method for a receiving device, comprising:

receiving a plurality of reference signals, and generating a plurality of channel estimates according to the plurality of reference signals;

generating at least one eigenvalue corresponding to the plurality of channel estimates according to the plurality of channel estimates;

generating a correlation correction value for compensating the plurality of channel estimates according to the at least one characteristic value;

generating a channel capacity according to the at least one characteristic value and the correlation correction value; and

based on the channel capacity, a modulation and coding scheme is determined.

9. The receiving method of claim 8, wherein the step of determining the modulation and coding scheme comprises:

generating bit efficiencies based on the channel capacities, an

The modulation and coding scheme is determined according to the bit efficiency.

10. The receiving method of claim 8, wherein the step of determining the modulation and coding scheme comprises:

generating condition numbers for the plurality of channels based on the at least one characteristic value, an

The correlation correction value is generated based on the condition number.