CN101399801A - Classification method for base station to determine mode for pre-coding matrix selection - Google Patents

Abstract

The invention discloses a classification method for the way of a Node B decision-making selection pre-coding matrix; the invention comprises: step S102, UE reports one or a plurality of PMIs to the Node B; step S104, the Node B judges whether the pre-coding matrix which one or a plurality of PMIs are corresponding to is reliable, the scheduling of the Node B and the channel correlation, and determines the way of the Node B decision-making selection pre-coding matrix according to the judging result; and step S106, the Node B marks the reserved part of a combination indicating bit according to the determined way of the Node B decision-making selection pre-coding matrix and sends the marked combination indicating bit to the UE. The invention can reduce the downlink control signaling overhead, thus effectively improving the system throughput.

Description

Classification method for the way the base station decides to select the precoding matrix

technical field

The present invention relates to the field of communications, and in particular, to a method for classifying the manner in which a base station decides to select a precoding matrix in a Multiple-Input Multiple-Out-put (MIMO) wireless mobile communication system.

Background technique

Orthogonal Frequency Division Multiplexing (OFDM) technology is essentially a multi-carrier modulation communication technology, and it is one of the core technologies in the fourth generation mobile communication.

In the frequency domain, the OFDM multipath channel exhibits frequency-selective fading characteristics. In order to overcome this fading, the channel is divided into multiple sub-channels in the frequency domain. The spectral characteristics of each sub-channel are approximately flat. Each OFDM sub-channel They are orthogonal to each other, so the spectrums of the sub-channels are allowed to overlap with each other, so that the spectrum resources can be utilized to the greatest extent.

In the OFDM wireless transmission system technology, in order to obtain greater data transmission throughput, frequency scheduling can be applied to data transmission. This is because the transmission channel of each user has different frequency-domain fading in different frequency bands, and in such a frequency band, the channel quality of each user may be different. Therefore, frequency domain scheduling can be used to schedule each frequency band to user equipment with better channel conditions, thereby optimizing system throughput.

MIMO technology can increase system capacity, improve transmission performance, and can be well integrated with other physical layer technologies, so it has become a key technology for B3G and 4G mobile communication systems. However, when the channel correlation is strong, the diversity gain and multiplexing gain brought by the multipath channel will be greatly reduced, which will cause a significant decline in the performance of the MIMO system. In recent years, a new MIMO precoding method has been proposed, in which the MIMO channel is transformed into multiple independent virtual channels through precoding processing at the transceiver end, so this method will be an efficient MIMO multiplexing method. Because the influence of channel correlation is effectively eliminated, the precoding technology ensures the stable performance of the MIMO system in various environments.

Long Term Evolution (LTE) is an important plan of the third generation partnership organization. The simplified process of precoding implemented in LTE is as follows: set the codebook (set of precoding matrices) in the user equipment (UE) and the base station (Node B), measure the downlink channel by the UE, and perform singular decomposition (SVD) on the channel matrix, Obtain the V matrix, and find the closest precoding matrix in the codebook, and then feed back the precoding matrix index (PrecodingMatrix Indicator, PMI) to the NodeB, and the NodeB looks for the corresponding precoding matrix in the codebook according to the received PMI, and in the downlink This precoding matrix is applied in transmission.

The precoding feedback is discussed in the LTE standard. The determined working assumption is that the limit is 2.5M. If the bandwidth is less than 2.5M, a PMI is calculated from the entire frequency band and fed back to the NodeB. If the bandwidth is greater than 2.5M, use continuous 4/5 /6 RBs (LTE defines resource blocks, frequency granularity 180kHz/RB) feed back a PMI to the NodeB. In order to prevent the index number sent by the UE uplink from the index number received by the NodeB (this will cause the precoding matrix used by the NodeB to transmit cannot be decoded correctly on the UE side, resulting in errors), it is very necessary to set the precoding codebook used by the NodeB Inform the UE in some way.

However, this will cause another problem. For the frequency selection precoding matrix, if each small-band NodeB transmits a PMI to the UE, the length of the downlink control signaling will be too large. For example, assuming that the bandwidth is 20M, every 5 RBs (1M bandwidth) transmits a PMI, there are 16 codebooks in total, and 4 bits are required to indicate the selected precoding matrix information, so a total of 80 bits of downlink overhead are required. Such a large overhead is unacceptable for future mobile communication systems whose main goal is to increase the data rate.

For the Node B to select the precoding matrix, if the Node B has a different selection strategy, it will be considered to make the Node B abandon the precoding matrix reported by the UE and select another precoding matrix, but this is only (based on channel conditions, etc.) ) is a last resort choice, and it is only a small probability event. Compared with full-band precoding feedback, the simulation results of some research structures show that the performance of frequency-selective precoding feedback with 4×4 antenna configuration (5RB frequency granularity, 180k/RB) is about 5% higher than that of the same time granularity full-band precoding system. It can be seen that under a small probability, the NodeB does not accept the precoding matrix fed back by the UE and selects the precoding matrix of the whole frequency band, which will not bring significant system performance degradation.

Therefore, it is necessary to inform the UE of the PMI used by the Node B through other methods that occupy less downlink signaling overhead.

Contents of the invention

The present invention is made in consideration of the above problems. Therefore, the main purpose of the present invention is to provide a classification scheme for base station decision-making and selection of precoding matrix, so as to reduce downlink control signaling overhead and improve system throughput.

According to an embodiment of the present invention, a method for classifying the manner in which a base station decides to select a precoding matrix is provided.

The method includes: step S102, the user equipment reports one or more precoding matrix indexes to the base station; step S104, the base station judges whether the precoding matrix corresponding to the one or more precoding matrix indexes is reliable, and according to the judgment result and the base station's Scheduling and channel correlation determine the way the base station decides to select the precoding matrix; and step S106, the base station identifies the predetermined part of the combination indicator bit according to the determined way of decision-making selection of the precoding matrix, and sends the identified combination indicator bit to user equipment.

Wherein, the manner in which the base station decides to select the precoding matrix includes: fully accepting one or more precoding matrix indexes sent by the user equipment, not accepting one or more precoding matrix indexes sent by the user equipment at all, and skipping the one or more precoding matrix indexes sent by the user equipment. One or more precoding matrix indices.

In addition, in the case that the base station completely accepts one or more precoding matrix indexes sent by the user equipment, the base station identifies a predetermined part of the combination indication bits as "00".

In the case that the base station does not accept one or more precoding matrix indexes sent by the user equipment at all, the base station identifies a predetermined part of the combination indication bits as "01". At this time, the method may further include: the base station selects all precoding matrix indexes used by the user equipment when reporting in the last period.

Finally, in the case that the base station skips one or more precoding matrix indexes sent by the user equipment, the base station identifies the predetermined part of the combination indication bits as "11". In this case, the method may further include that the base station reselects the precoding matrix index, and adds the reselected precoding matrix index to the combination indication bit.

In addition, the predetermined part of the above-mentioned combination indicating bits is the first two bits.

In addition, before step S102, it further includes: step S102-2, the user equipment decomposes the downlink channel matrix to obtain the V matrix; and step S102-4, the user equipment searches the codebook for the precoding matrix corresponding to the V matrix, And select the precoding matrix index of the found precoding matrix and report it to the base station.

Through the above technical solution of the present invention, the downlink control signaling overhead can be reduced, thereby effectively improving the system throughput.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention. In the attached picture:

FIG. 1 is a flow chart of a method for classifying the manner in which a base station decides to select a precoding matrix according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of combination indicator bits in a classification method for base station decision-making and selection of a precoding matrix according to an embodiment of the present invention; and

Fig. 3 is a flow chart of a processing example of a method for classifying the manner in which a base station decides to select a precoding matrix according to an embodiment of the present invention.

Detailed ways

In this embodiment, a method for classifying the manner in which a base station (Node B) decides to select a precoding matrix is provided. In this method, the Node B is divided into three ways of processing the PMI reported by the UE: (1) accepting the PMI reported by the UE, that is, the NodeB accepts the PMI corresponding to all frequency bands on the frequency band reported to it by all UEs; 2) Node B considers that the uplink transmission is unreliable according to the channel conditions. At this time, it can select the PMI weights corresponding to all frequency bands reported by the UE to the Node B in the previous period, and discard the possible error reported by the UE this time. PMI transmission weight; (3) Node B skips the PMI reported by UE, but selects another precoding matrix from the codebook according to certain criteria, such as channel criteria or scheduling criteria, and uses this as the whole Precoded transmit matrix over frequency band. This embodiment will be described in detail below.

As shown in Figure 1, according to the classification method of the Node B decision selection mode of the precoding matrix according to the present embodiment, the method includes: step S102, the UE reports one or more precoding matrix indexes (PMI) to the Node B; step S104, the Node B judges whether the precoding matrix corresponding to one or more PMIs is reliable, and determines the way Node B decides to select the precoding matrix according to the judgment result and NodeB's scheduling and channel correlation; and step S106, Node B selects according to the determined decision The predetermined part (preferably, the first two digits) of the combined indicator bits is identified by means of a precoding matrix, and the identified combined indicator bits are sent to the UE.

Wherein, the way of the Node B to decide to select the precoding matrix includes: completely accepting one or more PMIs sent by the UE, not accepting one or more PMIs sent by the UE at all, and skipping one or more PMIs sent by the UE.

In the case that the Node B fully accepts one or more PMIs sent by the UE, the Node B identifies the predetermined part of the combination indication bit as "00".

In the case that the Node B does not accept one or more PMIs sent by the UE at all, the Node B identifies the predetermined part of the combination indication bit as "01". At this time, the method may further include: the Node B selects all PMIs used by the UE for reporting in the last period.

Finally, in case the Node B skips one or more PMIs sent by the UE, the Node B identifies the predetermined part of the combined indicator bits as "11". In this case, the method may further include, that the Node B reselects the PMI, and adds the reselected PMI to the combination indication bit.

A specific identification manner may be shown in FIG. 2 . In FIG. 2 , the first two digits represent three ways for the UE to accept, not accept, and select another codebook. In addition, an indication mode is reserved. In the indication mode, the two-bit indication bit is followed by 4-bit PMI information (this number can be changed for codebooks of different sizes).

In addition, before step S102, it further includes: step S102-2, the UE decomposes the downlink channel matrix to obtain the V matrix; and step S102-4, the UE searches the codebook for the precoding matrix corresponding to the V matrix, and selects The found PMI of the precoding matrix is reported to the Node B.

This embodiment will be described below in combination with specific examples.

As shown in Figure 3, in specific implementation, the method according to this embodiment may include the following steps:

S300, the precoding feedback process starts;

S301. The UE performs SVD decomposition on the downlink channel matrix, and searches for the closest precoding matrix in the codebook according to the decomposed V matrix, and selects the PMI;

S302, the UE feeds back the selected PMI to the NodeB through an uplink channel;

S303, the NodeB judges the received PMI of each frequency band, if the PMI on all the frequency bands reported by the UE is accepted, then execute step S304; if the NodeB thinks that the uplink transmission of the UE is unreliable, execute the step S305; if the NodeB passes the UE Reported PMI and another selection of PMI codebook, then execute step S306;

S304, the NodeB accepts the PMIs of all the frequency bands reported by the corresponding UE, and uses (0, 0) in the combination indication bit to indicate and inform the UE of the information;

S305, the NodeB considers that the PMI reported by the UE is unreliable, and the NodeB can apply the corresponding ones on all frequency bands reported by the UE to the NodeB in the previous period, and discard the PMI indication accepted this time;

S306, the NodeB ignores the PMI fed back to it by the UE, but applies the same transmit precoding matrix for the whole frequency band and informs the UE. The 4-bit PMI indication follows the two-bit PMI indication;

S307, the UE receives various acceptance indications and full-band PMIs sent by the NodeB to the UE, and the process ends.

In summary, compared with the existing method of transmitting all PMIs on the full frequency band in the downlink, the present invention uses a 2-bit combination to indicate whether the PMI is accepted by the NodeB for the type of NodeB decision, which can reduce the overhead of downlink control signaling and improve The purpose of system throughput.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. the sorting technique of the mode of a base station to determine selection pre-coding matrix is characterized in that, comprising:

Step S102, subscriber equipment reports the base station with one or more pre-coding matrix indexes;

Step S104, described base station judges whether the pre-coding matrix of described one or more pre-coding matrix index correspondences is reliable, and according to the scheduling and the channel relevancy of judged result and described base station, determines that described base station to determine selects the mode of pre-coding matrix; And

Step S106, described base station selects the mode of pre-coding matrix that the predetermined portions that makes up indicating bit is identified according to the described decision-making of determining, and the combination indicating bit after will identifying sends to described subscriber equipment.

2. sorting technique according to claim 1, it is characterized in that described base station to determine selects the mode of pre-coding matrix to comprise: described one or more pre-coding matrix indexes of accept described one or more pre-coding matrix indexes of described subscriber equipment transmission fully, not accepting described one or more pre-coding matrix indexes of described subscriber equipment transmission and skip described subscriber equipment transmission fully.

3. sorting technique according to claim 2, it is characterized in that, accept fully in described base station under the situation of described one or more pre-coding matrix indexes that described subscriber equipment sends, described base station is designated " 00 " with the described predetermined portions of described combination indicating bit.

4. sorting technique according to claim 2, it is characterized in that, do not accept fully in described base station under the situation of described one or more pre-coding matrix indexes that described subscriber equipment sends, described base station is designated " 01 " with the described predetermined portions of described combination indicating bit.

5. sorting technique according to claim 4 is characterized in that, further comprises: employed all pre-coding matrix indexes give the correct time on described base station selected described subscriber equipment carried out in the last cycle.

6. sorting technique according to claim 2, it is characterized in that, skip in described base station under the situation of described one or more pre-coding matrix indexes that described subscriber equipment sends, described base station is designated " 11 " with the described predetermined portions of described combination indicating bit.

7. sorting technique according to claim 6 is characterized in that, further comprises, pre-coding matrix index is reselected in described base station, and the described pre-coding matrix index of reselecting is added in the described combination indicating bit.

8. according to each described sorting technique in the claim 3 to 7, it is characterized in that the described predetermined portions of described combination indicating bit is preceding two positions.

9. according to each described sorting technique in the claim 1 to 6, it is characterized in that, before described step S102, further comprise:

Step S102-2, described subscriber equipment decomposes the down channel matrix, obtains the V matrix; And

Step S102-4, described subscriber equipment search in code book and the corresponding pre-coding matrix of described V matrix, and select the pre-coding matrix index of the described pre-coding matrix find to report described base station.

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