WO2012100452A1

WO2012100452A1 - Scheduling method and apparatus for multi-user multi-input multi-output

Info

Publication number: WO2012100452A1
Application number: PCT/CN2011/071999
Authority: WO
Inventors: 余秋星; 刘�东; 陈琼
Original assignee: 中兴通讯股份有限公司
Priority date: 2011-01-24
Filing date: 2011-03-21
Publication date: 2012-08-02
Also published as: CN102611535A

Abstract

A scheduling method for multiuser multi-input multi-output（MU-MIMO） is disclosed in the present invention. The method includes: selecting a first user from users to be paired; from the users to be paired except the first user, selecting a second user, the frequency shift value of which and the frequency shift value of the first user meet a preset condition, to pair with the first user, wherein, users to be paired initially comprise all the users, after at least one time of pairing is completed, users to be paired comprise the other users except users which have been paired. The present invention also discloses a scheduling apparatus for MU-MIMO. The method greatly decreases computation complexity for user pairing.

Description

Multi-user multiple input multiple output scheduling method and device

TECHNICAL FIELD The present invention relates to the field of wireless communication technologies, and in particular, to a method and apparatus for scheduling multi-user multiple input multiple output.

Background technique

Multiple-input Multiple-output (MIMO) technology achieves spatial diversity gain by using multiple antenna transmissions and multiple antenna receptions to combat the effects of wireless fading channels. MIMO technology greatly improves the system capacity and spectrum efficiency of wireless communication systems and is a key technology for next-generation mobile communications. The general demand for smaller and lighter devices in future mobile communications will limit the number of antennas at the terminal, making the advantages of MIMO technology difficult to fully exploit in upstream transmissions. In order to solve this problem, a plurality of users transmitting a single antenna and a plurality of antennas of a base station can constitute a multi-user MIMO (Multi-User MIMO), thereby increasing the capacity of the uplink channel. MU-MIMO technology has also been adopted by the Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE) communication standards.

The transmission between users in MU-MIMO is independent of each other and can share the same uplink time-frequency resources. The base station pairs the users sent by the two single antennas according to the characteristics of the spatial channel, and allocates them to the same time-frequency resource, and the paired users need to send mutually orthogonal reference signals to obtain the data demodulation station through channel estimation. Required channel information. The signals received by the base station are different from each other through different channels, and the degree of mutual interference between users is different. Therefore, only the user pairing by a reasonable multi-user scheduling method makes it easier for the base station to separate the two transmitted signals. Proper demodulation is done to effectively increase system throughput. Since the base station needs to pair two users to form a MU-MIMO transmission according to a certain scheduling method, the scheduling method involved may have a large impact on the system. Normally, two users with better channel orthogonality are paired, so that it is easier to separate the two transmitted signals at the receiving end, but since the pairing is performed in all users in the cell, the computational complexity is high. ; paired at the same time The difference between the user's frequency offset is not considered in the process. After the large difference in the frequency offset of the paired users, the pilots or data of the two users cannot be separated at the same time by compensating the frequency offset of the two users. In addition to its unique Inter Access Inference (MAI), the user MIMO system also has its own serious Inter-Carrier Inference (ICI), which causes demodulation errors and throughput. decline. Even if such user pairing constitutes MU-MIMO, the complexity of receiver processing will increase dramatically, or the signaling overhead of the system will increase significantly. This frequency offset includes the Doppler frequency offset caused by the movement of the user terminal and the frequency offset caused by the crystal oscillator, which is inevitable.

SUMMARY OF THE INVENTION The technical problem to be solved by the present invention is to provide a scheduling method and apparatus for MU-MIMO, so as to achieve the technical complexity of reducing user pairing and improving the throughput of the MU-MIMO system. In order to solve the above problem, the present invention provides a multi-user multiple input multiple output scheduling method, the method includes: selecting a first user among users to be paired, and selecting a frequency among users to be paired except the first user And the second user that meets the preset condition between the bias value and the frequency offset value of the first user is paired with the first user, where the user to be paired initially includes all users, at least once

The step of selecting a second user includes: determining, in a user to be paired other than the first user, a set of users that meet a preset condition between a frequency offset value and a frequency offset value of the first user, according to a preset A pairing algorithm selects the second user from the set of users. among them:

The preset condition includes: an absolute value of a difference between a frequency offset value of the second user and the first user does not exceed a preset frequency offset threshold. The frequency offset threshold is determined according to the modulation coding mode and/or the signal to interference and noise ratio of the first user. The method further includes: After all users are paired, each user is notified to perform data transmission; and each user is received to transmit data, and frequency offset compensation is performed for each user pair in the time domain. The steps of performing frequency offset compensation for each user pair in the time domain include:

Offset compensation, or, using data transmission in the same time slot, and multiple users whose frequency offset is within a preset range, perform frequency offset compensation on the average of the frequency offset values of the included users . In order to solve the above problem, the present invention further provides a multi-user multiple input multiple output scheduling device, the device comprising: a pairing unit, configured to: select a first user among users to be paired, except for the first user And the second user that meets the preset condition between the frequency offset value and the frequency offset value of the first user is paired with the first user, where the user to be paired initially includes all user. The pairing unit is configured to select the second user in the following manner: in the user to be paired except the first user, determine a user set that satisfies a preset condition between the frequency offset value and the frequency offset value of the first user And selecting the second user from the set of users according to a preset pairing algorithm. The preset condition includes: the absolute value of the difference between the frequency offset values of the second user and the first user does not exceed a preset frequency offset threshold. The pairing unit is further configured to: determine the frequency offset threshold according to a modulation coding manner and/or a signal to interference and noise ratio of the first user. The device also includes:

a notification unit, configured to notify each user pair of data transmission after pairing all users ends; and a compensation unit configured to: receive data sent by each user pair, and forward each user in a time domain Line frequency offset compensation. The compensation unit is configured to perform frequency offset compensation compensation for each user pair in the time domain as follows, or use data transmission in the same time slot, and the frequency offset difference is within a preset range. The user performs frequency offset compensation on the plurality of user pairs on the average of the frequency offset values of the included users.

The invention determines the set of the second user paired with the first user according to the frequency offset value of the first user to be paired, which greatly reduces the computational complexity of the user pairing, and makes the frequency offset value of the paired user within a preset range. Internally, it is convenient for the receiver to perform frequency offset compensation for the paired user; pre-frequency offset compensation for the received paired user transmission signal can greatly reduce the MAI and ICI, solve the correctness of the demodulation of the currently paired user, and improve the scheduling. Effectiveness, enabling the system to achieve higher throughput.

1 is a flowchart of a MU-MIMO scheduling method according to an embodiment of the present invention; and FIG. 2 is a block diagram of a MU-MIMO scheduling apparatus according to an embodiment of the present invention.

Preferred embodiment of the invention

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in the case of no conflict, the features in the embodiments and the embodiments in the present application may be arbitrarily combined with each other. The present invention provides a scheduling method for MU-MIMO, the method comprising:

Selecting a first user among users to be paired, and selecting, among the users to be paired, other than the first user, a second user that meets a preset condition between a frequency offset value and a frequency offset value of the first user a first user pairing, wherein the user to be paired initially includes all users, at least once

After the pairing of all users is completed, each user is notified to perform data transmission; Receive data transmitted by each user pair, and perform frequency offset compensation for each user pair in the time domain. The selecting the second user includes: determining, among the users to be paired, other than the first user, a set of users that meet a preset condition between the frequency offset value and the frequency offset value of the first user, according to a preset pairing algorithm. Selecting the second user from the set of users. The specific pairing algorithm is described in the following embodiments. The preset condition includes: an absolute value of a difference between a frequency offset value of the second user and the first user does not exceed a preset frequency offset threshold. The frequency offset threshold may also be determined based on other conditions, such as the modulation coding mode and/or the signal to interference and noise ratio of the second user and the first user. The performing frequency offset compensation for each user pair in the time domain includes: using each user to perform data transmission in a time slot, and the frequency offset is within a preset range, and the frequency of the included user is used by multiple users. The average of the partial values compensates for the frequency offset of the plurality of user pairs. The implementation of the technical solution will be further described in detail below with reference to the accompanying drawings. The embodiments of the present invention can be applied to a wireless communication system supporting MU-MIMO such as an LTE system and a WiMAX system. The LTE system is taken as an example. FIG. 1 is a schematic flowchart of a basic MU-MIMO scheduling method according to an embodiment of the present invention. The process of the embodiment may be implemented by a base station, and the method includes the following steps:

S101. The base station determines a user set A and a frequency offset threshold. Specifically, for the case of the initial pairing, the user set A is all users in the cell, and frequency offset measurement and signal to interference and noise ratio measurement are required for all users in the user set A. For the case of non-primary pairing, the user set A is the updated user set in step S105. Then, according to the signal to interference and noise ratio, the corresponding modulation and coding mode is mapped, and the base station can determine the corresponding frequency offset threshold according to each modulation and coding mode, and the base station can also group the supported modulation and coding modes, and each group corresponds to one frequency. Partial threshold. The base station can also determine the frequency offset threshold directly according to the signal to interference and noise ratio. Preferably, the same modulation method uses a frequency offset threshold to reduce complexity. 5102. The base station selects a first user from the set A. Specifically, the existing algorithm can be used to select the first user. If the user with good service environment and good channel quality is prioritized, the first user is selected in the set A by using the maximum signal to interference ratio algorithm; if the fairness of the scheduling time is prioritized, the round robin algorithm is used (Round Robin) The first user is selected in the set A; if the throughput and fairness of the user are prioritized, the first user is selected in the set A using a proportional fairness algorithm or an improved proportional fairness algorithm. The algorithm has a detailed solution and will not be described here. The invention is not limited thereto, and the first user may also be randomly selected.

5103. Determine a user set for user pairing with the first user: 8. Specifically, the user set B is determined by: selecting a corresponding frequency offset threshold according to the modulation coding mode or the signal to interference and noise ratio of the first user determined in S102, and selecting a user from the user set A. That is, the user of the user set B is determined according to the formula (1): arg \ f _k - fi \< fnreshoid ( 1 )

k K,k≠i

In the above formula, for the frequency offset threshold value of the first user, f _k is the frequency offset value of the user k ( k ≡ K , K is the user index set in the user set , ), and the index of the first user is . From the formula (1), all users of the user set B satisfying the condition can be obtained.

5104. In the user set B, select a second user to pair with the first user. Specifically, among all the users of the user set B, the second user is selected for pairing. The second user may be selected by using a certain pairing algorithm, which may be an orthogonal pairing method, a determinant pairing method, and a post-processing signal-to-noise ratio matching method, etc., where the user matching algorithm has been used. Detailed solutions are not described here. Since the number of users included in the user set B is generally much smaller than the number of all users in the cell, this greatly reduces the complexity of selecting the second user. The pairing algorithm is not limited in the present invention, and the second user may be randomly selected. Assume that the second user is user j.

5105, Update user set A. Specifically, the manner of updating the user set A is the paired user determined by S102 S104 (user And user j) is removed from collection A.

S106. Determine whether the user pairing ends. If the pairing has not ended, steps S102 to S105 are repeated to perform the next user pairing operation. If the pairing ends, step S107 is performed. S107. The base station notifies each user to perform data transmission. Specifically, the base station notifies each user pair to perform data transmission by signaling, and each user pair transmits data on respective time-frequency resources, and different users occupy different time-frequency resources.

S108: After receiving the data sent by each user, the base station performs frequency offset compensation on each user pair in the time domain before demodulation. Specifically, the compensated frequency offset value is an average of the frequency offset values of the two users included by the user. Alternatively, a plurality of users who perform data transmission in the same time slot and whose frequency offset is within a preset range perform frequency offset compensation on the plurality of user pairs on the average of the frequency offset values of the included users. The invention performs frequency offset compensation in the time domain. After the compensation, the residual frequency offset is considered to be small, and the frequency offset is not processed in the channel estimation, the channel estimation processing can be simplified, and the performance can be guaranteed. In addition, through the frequency offset compensation, the residual frequency offset is greatly reduced, the MAI and ICI can be greatly reduced, and the demodulation capability for the paired users is improved. FIG. 2 is a MU-MIMO scheduling apparatus according to an embodiment of the present invention, where the apparatus includes: a pairing unit, configured to: select a first user among users to be paired, among users to be paired except the first user And the second user that meets the preset condition between the frequency offset value and the frequency offset value of the first user is paired with the first user, where the user to be paired initially includes all users;

a notification unit, configured to: notify each user pair of data transmission after pairing all users ends; and a compensation unit, configured to: receive data sent by each user pair, and perform frequency offset compensation for each user pair in the time domain . The pairing unit is configured to select the second user in the following manner: in the user to be paired except the first user, determining that the preset value is met between the frequency offset value and the frequency offset value of the first user The user set selects the second user from the set of users according to a preset pairing algorithm. The preset condition includes: an absolute value of a difference between a frequency offset value of the second user and the first user does not exceed a preset frequency offset threshold. The pairing unit is further configured to: determine the frequency offset threshold according to a modulation coding manner and/or a signal to interference and noise ratio of the first user. The compensation unit is configured to perform frequency offset compensation on the user pair by using an average value of frequency offset values of two users included in each user pair, or use data transmission in the same time slot, and A plurality of users whose frequency offset is within a preset range perform frequency offset compensation on the plurality of user pairs on the average of the frequency offset values of the included users. The embodiment of the present invention determines the set of the second user paired with the first user according to the frequency offset value of the first user to be paired, which greatly reduces the computational complexity of the user pairing, and makes the frequency offset value of the paired user preset. Within the scope, it is convenient for the receiver to compensate the paired user for frequency offset; pre-frequency offset compensation for the received paired user data can greatly reduce the MAI and ICI, and improve the correctness of the paired user demodulation and improve The effectiveness of the scheduling enables the system to achieve higher throughput. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device, or they may be separately fabricated into individual integrated circuit modules, or they may be Multiple modules or steps are made into a single integrated circuit module. Thus, the invention is not limited to any particular hardware and software. Piece combination.

INDUSTRIAL APPLICABILITY The present invention determines a set of second users to be paired with according to a frequency offset value of a first user to be paired, which greatly reduces computational complexity of user pairing, and causes a frequency offset value of the paired user to be preset Within the scope of the range, it is convenient for the receiver to perform frequency offset compensation for the paired user; pre-frequency offset compensation for the received paired user transmission signal can greatly reduce the MAI and ICI, and solve the correctness of the demodulation of the currently paired user, and improve The effectiveness of the scheduling enables the system to achieve higher throughput.

Claims

Claim

1. A multi-user multiple input multiple output scheduling method, the method comprising:

2. The method according to claim 1, wherein the step of selecting the second user comprises: determining, between the users to be paired except the first user, that the frequency offset value is satisfied with the frequency offset value of the first user The set of users of the preset condition selects the second user from the set of users according to a preset pairing algorithm.

3. The method according to claim 1, wherein: the preset condition comprises: an absolute value of a difference between a frequency offset value of the second user and the first user does not exceed a preset frequency offset threshold .

The method according to claim 3, wherein the frequency offset threshold is determined according to a modulation coding mode and/or a signal to interference and noise ratio of the first user.

The method according to any one of claims 1 to 4, further comprising: notifying each user pair of data transmission after pairing all users ends;

Receive data transmitted by each user pair, and perform frequency offset compensation for each user pair in the time domain.

The method according to claim 5, wherein the step of performing frequency offset compensation for each user pair in the time domain comprises:

Offset compensation, or, using data transmission in the same time slot, and multiple users whose frequency offset is within a preset range, perform frequency offset compensation on the average of the frequency offset values of the included users .

7. A multi-user multiple input multiple output scheduling device, the device comprising:

a pairing unit, configured to: select a first user among the users to be paired, and select a preset condition between the selected frequency offset value and the frequency offset value of the first user among the users to be paired except the first user The second user is paired with the first user, wherein the user to be paired initially includes all users.

The device according to claim 7, wherein the pairing unit is configured to select the second user in the following manner: determining, in a user to be paired other than the first user, a frequency offset value and the first user The set of users satisfying the preset condition between the frequency offset values, and selecting the second user from the set of users according to a preset pairing algorithm.

9. The apparatus according to claim 7, wherein: the preset condition comprises: an absolute value of a difference between a frequency offset value of the second user and the first user does not exceed a preset frequency offset threshold .

10. The apparatus according to claim 9, wherein the pairing unit is further configured to: determine the frequency offset threshold according to a modulation coding mode and/or a signal to interference and noise ratio of the first user.

The apparatus according to any one of claims 7 to 10, further comprising: a notification unit configured to notify each user pair of data transmission after pairing all users ends; and a compensation unit Set to: Receive data sent by each user pair, and perform frequency offset compensation for each user pair in the time domain.

12. The apparatus according to claim 11, wherein the compensation unit is configured to perform frequency offset compensation for each user pair in the time domain as follows: using a frequency offset value of two users included in each user pair The average value is used to compensate the user pair for frequency offset, or the average value of the frequency offset values of the users included in the data transmission in the same time slot and the frequency offset difference is within a preset range. The plurality of user pairs perform frequency offset compensation.