CN102056311B - Base station scheduling method for improving MU-MIMO performance and device - Google Patents

Abstract

The present invention relates to a base station scheduling method for improving MU-MIMO performance, comprising: Step 1: Each user equipment feeds back a precoding matrix index and a channel quality indicator at time t+1 to the base station side, and the base station side estimates each user equipment t+1 The precoding matrix at moment 1; step 2: the base station side pairs the user equipment, and calculates the value of the determinant of the difference between the feedback precoding matrix group of the paired two user equipment and the precoding matrix group estimated by the base station side; step 3: If the value is greater than or equal to 1, the sending rates of the two paired user equipments are both zero; The absolute value of the difference between the rate multiplied by 1 and the stated value. The present invention comprehensively considers CQI, PMI and CSI during scheduling, effectively avoids severe inter-user interference, and better improves MU-MIMO performance.

Description

Base station scheduling method and device for improving MU-MIMO performance

Technical Field

The invention relates to the field of communication technology base station scheduling, in particular to a base station scheduling method and device of an MU-MIMO system in an LTE TDD system.

Background

The Long Term Evolution project (LTE) improves and enhances the 3G air access technology, and adopts OFDM and MIMO as the only standard of the wireless network Evolution. The peak rates of 100Mbit/s at the downlink and 50Mbit/s at the uplink can be provided under the 20MHz spectrum bandwidth. The performance of cell edge users is improved, the cell capacity is improved and the system delay is reduced. LTE defines two ways of LTE FDD (Frequency Division Duplexing) Frequency Division Duplexing and LTE TDD (time Division Duplexing) time Division Duplexing at the same time.

The channel model of the LTE system is: suppose that a downlink received signal is at time t $y_t=H_t{\hat{V}}_t{s}_t+n_t,$ Wherein y is_tFor receiving signals at time t, H_tIn order to be a matrix of channels,

is the precoding matrix of the transmitting end, s_tIs a transmission signal, n_tIs AWGN noise with variance N. s_tHas a transmission power of P_tThe modulation and coding scheme adopted is M_t. Wherein,

the selection of the base station side is comprehensively determined according to the feedback of the transmitting end and the channel information acquired by some base station sides. For MU-MIMO (multi-user-multiple input output) and SU-MIMO (single user-multiple input output) systems, the feedback form of the User Equipment (UE) is the same, and it is necessary to feed back the Channel Quality Indicator (CQI) and the channel Precoding Matrix Index (PMI) of one data stream. And the base station side carries out scheduling according to the fed-back CQI and the PMI.

For the LTE TDD system, the base station side can obtain part of the downlink Channel State Information (CSI) by using channel reciprocity, and therefore, the base station side should use the precoding matrix for the next time

Can be estimated as

However, due to many factors, the channel information obtained by the base station side is not very accurate and cannot be directly usedAs

It also needs to comprehensively consider the precoding matrix corresponding to PMI feedback

And CQI_t+1。

And because for MU-MIMO, each user uses one data stream, there is a problem of inter-user interference. The serious interference among users can reduce the system capacity greatly. Since power control is not employed between data streams of two users in the LTE system, the transmission data power of the two users is the same. If the inter-user interference is severe, the actual received signal-to-noise ratio is low even if the user has a very good channel quality. Therefore, a joint scheduling method that can improve MU-MIMO performance and comprehensively considers CQI, PMI, and CSI is required.

Disclosure of Invention

Aiming at the defects and shortcomings in the prior art, the invention aims to provide a base station scheduling method and a base station scheduling device for improving MU-MIMO performance, which can comprehensively consider CQI, PMI and CSI and better improve the MU-MIMO performance.

In order to achieve the above object, the present invention provides a base station scheduling method for improving MU-MIMO performance, including:

step 1: each user equipment feeds back a precoding matrix index and a channel quality indicator at the t +1 moment to the base station side, and the base station side estimates a precoding matrix at the t +1 moment of each user equipment; wherein the precoding matrix index corresponds to a feedback precoding matrix, the channel quality indicator corresponds to a nominal transmission rate, and t is an arbitrary time;

step 2: the base station side pairs the user equipment, and calculates the determinant value of the difference between the feedback precoding matrix group of the two paired user equipment and the precoding matrix group estimated by the base station side;

and step 3: if the value is greater than or equal to 1, the sending rates of the two paired user equipment are both zero;

if the value is less than 1, the sending rates of the two paired user equipments are corrected to be respectively: the nominal transmission rate of each user equipment is multiplied by the absolute value of the difference between 1 and said value.

Preferably, after correcting the transmission rate, the base station side selects the feedback precoding matrix group or the precoding matrix group estimated by the base station side as a precoding matrix group.

Preferably, the base station side estimates the precoding matrix at the time t +1 by using the channel reciprocity to obtain partial downlink channel state information.

The invention also provides a base station scheduling device for improving MU-MIMO performance, which comprises:

a feedback module, configured to feed back, to a base station side, a precoding matrix index and a channel quality indicator at a time t +1 by each ue, where the precoding matrix index corresponds to a feedback precoding matrix, the channel quality indicator corresponds to a nominal sending rate, and t is any time;

the estimation module is used for estimating a precoding matrix of each user equipment at the t +1 moment by the base station side;

the pairing module is used for pairing the user equipment at the base station side and calculating the determinant value of the difference between the feedback precoding matrix group of the two paired user equipment and the precoding matrix group estimated at the base station side;

the processing module is used for determining that the sending rates of the two paired user equipment are both zero when the value calculated by the pairing module is greater than or equal to 1;

when the value calculated by the pairing module is less than 1, the transmission rates of the two paired user equipments are corrected to be respectively: the nominal transmission rate of each user equipment is multiplied by the absolute value of the difference between 1 and said value.

Preferably, after correcting the transmission rate, the base station side selects the feedback precoding matrix group or the precoding matrix group estimated by the base station side as a precoding matrix group.

Preferably, in the above technical solution, the estimating module estimates the precoding matrix at the time t +1 by using channel reciprocity to obtain partial downlink channel state information at the base station side.

The method and the device provided by the invention utilize the corrected rate pairing to carry out relevant scheduling, can effectively avoid the scheduling of users with serious interference among the users, and can improve the accuracy of system transmission to a certain extent by correcting the rate. Therefore, the system performance of the LTE-TDD system applying the MU-MIMO technology can be improved.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings. The above and other objects, features and advantages of the present invention will be apparent to those skilled in the art from the detailed description of the present invention.

Drawings

Fig. 1 is a schematic diagram of a preferred embodiment of a base station scheduling method for improving MU-MIMO performance according to the present invention;

fig. 2 is a schematic diagram of a base station scheduling apparatus for improving MU-MIMO performance according to a preferred embodiment of the present invention.

Detailed Description

As shown in fig. 1, a preferred embodiment of a method for scheduling a base station to improve MU-MIMO performance according to the present invention includes:

step 11: each user equipment UE feeds back a precoding moment at time t +1 (t is an arbitrary time) to the base station sideArray index PMI, channel quality indicator CQI, generally, one PMI corresponds to one feedback precoding matrix

One channel quality indicator CQI_t+1Corresponding to a nominal transmission rate T_t+1；

Step 12: the base station side estimates a precoding matrix at the t +1 moment by obtaining part of downlink Channel State Information (CSI) through channel reciprocity

Step 21: the base station side pairs the user equipment, wherein, the user equipment m is assumed to be paired with the user equipment n;

step 22: calculating feedback precoding matrix groups of the two paired user equipments $\stackrel{\→}{V_{\mathrm{mn}}}=[\stackrel{\→}{V_{t+1}^m},\stackrel{\→}{V_{t+1}^n}]$ Precoding matrix group with base station side estimation

Value of determinant of difference between

And step 3: if the value is greater than or equal to 1, it indicates that there is serious inter-user interference between the two paired user equipments, and therefore the sending rates of the two user equipments are both zero;

if the value D in the above embodiment is_mnIf the number of the user equipment is less than 1, the interference between the two paired user equipment is acceptable, the pairing is successful, but the D can be calculated_mnThe sending rate of the user equipment is corrected, the corrected rate is used for carrying out relevant scheduling, the accuracy of system transmission can be improved to a certain extent, and the sending rates of the user equipment which is matched in a correcting way are respectively as follows: the nominal sending rate of each user equipment is multiplied by the absolute value of the difference between 1 and the value, that is, the channel quality information fed back by the user equipment at the t +1 moment is assumed to be CQI_t+1Then the corresponding nominal transmission rate is s_t+1Then the transmission rate pair after pairing of user equipment m and user equipment n is [ s ]_t+1 ^m，s_t+1 ⁿ]According to D calculated in step 2_mnThe transmission rate pair is modified to:

$[s_{t+1}^{m^{\′}},s_{t+1}^{n^{\′}}]=[s_{t+1}^m(1-D_{\mathrm{mn}}),s_{t+1}^n(1-D_{\mathrm{mn}})]$

in the above embodiment, after correcting the transmission rate, the base station side may select the feedback precoding matrix groupAs the precoding matrix group, a precoding matrix group estimated on the base station side may be selected

As a precoding matrix set.

In step 1 of the above embodiment, a specific method for estimating a precoding matrix at a time t +1 by a base station side obtaining partial downlink channel state information by using channel reciprocity includes: the base station side obtains the channel response H at the t moment through the channel estimation of the uplink pilot frequency at the t moment_tBy the pair H_tPerforming SVD to obtain H_tThe precoding matrix at time t +1 may be the conjugate transpose of V, i.e. UAV ${\tilde{V}}_{t+1}=V^{*}.$

As shown in fig. 2, a preferred embodiment of a base station scheduling apparatus for improving MU-MIMO performance according to the present invention includes: a feedback module 101, an estimation module 102, a pairing module 103, and a processing module 104, wherein:

the feedback module 101 is configured to feedback, to the base station side, a precoding matrix index and a channel quality indicator at a time t +1, where the precoding matrix index corresponds to a feedback precoding matrix, the channel quality indicator corresponds to a nominal sending rate, and t is any time;

the estimation module 102 is configured to estimate, at the base station side, a precoding matrix at a time t +1 of each user equipment;

the pairing module 103 is configured to pair the user equipment at the base station side, and calculate a determinant value of a difference between a feedback precoding matrix group of the two paired user equipment and a precoding matrix group estimated at the base station side;

the processing module 104 is configured to, when the value calculated by the pairing module is greater than or equal to 1, determine that the sending rates of the paired two pieces of user equipment are both zero;

when the value calculated by the pairing module is smaller than 1, correcting the sending rates of the two paired user equipment to be respectively: the nominal transmission rate of each user equipment is multiplied by the absolute value of the difference between 1 and said value.

After correcting the transmission rate, the base station side may select the feedback precoding matrix group or the precoding matrix group estimated by the base station side as a precoding matrix group.

In the estimation module 102, the base station side estimates the precoding matrix at the time t +1 by using the channel reciprocity to obtain the state information of part of the downlink channels.

Although the present invention has been clearly illustrated by the above embodiments and the accompanying drawings, it is apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention, and it is intended to cover all such changes and modifications as fall within the scope of the appended claims.

Claims (6)

1. A base station scheduling method improving MU-MIMO performance, characterized in that, comprising: Step 1: Each user equipment feeds back the precoding matrix index and channel quality indicator at time t+1 to the base station side, and the base station estimates the precoding matrix at time t+1 of each user equipment; wherein, the precoding matrix index corresponds to Feedback a precoding matrix, the channel quality indicator corresponds to a nominal transmission rate, and t is any time; Step 2: The base station side pairs the user equipment, and calculates the value of the determinant of the difference between the feedback precoding matrix group of the paired two user equipment and the precoding matrix group estimated by the base station side; Step 3: If the value is greater than or equal to 1, the sending rates of the two paired user equipments are both zero; If the value is less than 1, the sending rates of the paired two user equipments are corrected respectively: the absolute value of the difference between the nominal sending rate of each user equipment multiplied by 1 and the said value. 2. The base station scheduling method according to claim 1, wherein after the transmission rate is corrected, the base station side selects the feedback precoding matrix group or the precoding matrix group estimated by the base station side as the precoding matrix group. 3. The base station scheduling method according to claim 1, wherein the base station uses channel reciprocity to obtain part of the downlink channel state information to estimate the precoding matrix at time t+1. 4. A base station scheduling device for improving MU-MIMO performance, characterized in that it comprises: The feedback module is used for each user equipment to feed back the precoding matrix index and channel quality indicator at time t+1 to the base station side, wherein the precoding matrix index corresponds to the feedback precoding matrix, and the channel quality indicator corresponds to Nominal sending rate, t is any time; The estimation module is used for the base station side to estimate the precoding matrix of each user equipment at time t+1; The pairing module is used to pair the user equipment on the base station side, and calculate the value of the determinant of the difference between the feedback precoding matrix group of the paired two user equipment and the precoding matrix group estimated by the base station side; A processing module, configured to: when the value calculated by the pairing module is greater than or equal to 1, the sending rates of the paired two user equipments are both zero; When the value calculated by the pairing module is less than 1, correcting the sending rates of the paired two user equipments is: the absolute value of the difference between the nominal sending rate of each user equipment multiplied by 1 and the said value. 5. The base station scheduling device according to claim 4, wherein after the transmission rate is corrected, the base station side selects the feedback precoding matrix group or the precoding matrix group estimated by the base station side as the precoding matrix group. 6 . The base station scheduling device according to claim 4 , wherein the estimating module uses channel reciprocity to obtain part of the downlink channel state information on the base station side to estimate the precoding matrix at time t+1. 7 .

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