CN101400074A - Method, user equipment and system for reducing feedback quantity of pre-coding matrix index number - Google Patents
Method, user equipment and system for reducing feedback quantity of pre-coding matrix index number Download PDFInfo
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Abstract
Disclosed is a method of reducing precoding matrix index number feedback quantity, a user equipment and a communication system, used for the technical field of wireless transmission. The user equipment of the invention adopts the corresponding feedback mode of the precoding matrix index number according to different frequency selective characteristics of the channel, feeds back the precoding matrix index number of the whole bandwidth and the precoding matrix index number of the selected sub-band; the user equipment feeds back the sub-band serial number required to feed back, the channel quality indication information and the precoding matrix index number to a base station through an up link; the base station performs transmitter optimization according to the information fed back by the user equipment, thereby increasing the performance of the system under the premise of compromising the service quality of the wireless district. The invention provides an information feedback method of reducing precoding matrix index number feedback quantity in the up link, performs feedback with high efficiency and simpleness on the information of the down link through unique method, thereby reducing air cost in the up link, saving frequency spectrum resource and increasing the system performance.
Description
Technical field
The present invention relates to a kind of information feedback method of radio communication, can in up link, reduce feedback quantity of pre-coding matrix index number, be used for radio transmission technical field.
Background technology
Fast development along with wireless traffic, the number of subscriber equipment also exponentially shape increases, can provide two-forty and high performance service for numerous subscriber equipmenies but the main challenge that wireless traffic faced still is a wireless traffic, people's expectation improves the capacity of wireless area by OFDM (OFDM) technology and multi-input/output antenna (MIMO) technology.Therefore, the data throughout of raising wireless area becomes the important indicator of weighing the radio cells quality.The IMT2000 standardization has been considered to adopt the MIMO technology in the third generation partner planning item (3GPP), because MIMO can obtain high data throughout.In the 3G (Third Generation) Moblie technology, base station (BS) utilized the channel condition information (CSI) of subscriber equipment (UE) feedback, changes the transmission data rate of base station transmitter by adaptive coding modulation.At present, to use the feedback information of subscriber equipment to come that transmitter is optimized design all the fashion with the thought and the method that improve the availability of frequency spectrum in the base station in super three generations (S3G) cell mobile communication systems, IEEE802.16 system and the WiMAX wireless local area network (WLAN) system of LTE (Long Term Evolution) definition, the MIMO transmission method that therefore many companies propose based on precoding, be closed-loop policy, it allows to adopt channel feedback information to improve the performance of system.But, if the link information of each subscriber equipment feedback is too many, the order (Rank) that comprises MIMO, pre-coding matrix index number (PMI), channel quality indication (CQI), whole feedback informations will be very huge data, can increase the weight of the aerial expense of up based on feedback link undoubtedly greatly, cause the reduction of the availability of frequency spectrum of up link, thereby it is serious to the service quality (QoS) that influences wireless area, therefore, how do not damage or minimum the basis of damaging the closed-loop MIMO system performance on reduce feedback information amount of information will be an important proposition in the research closed loop precoding MIMO system.Set up a kind of compromise and balance just aloft between feedback overhead and the closed-loop MIMO performance based on the information feedback method of code book.A kind of trial and the effort of and balance compromise by the design and use above-mentioned just foundation of information feedback method flexibly.The excellent information feedback method can reduce the aerial expense of feedback information and not damage or minimum the closed-loop MIMO system performance of damaging, therefore, can utilize channel in the characteristic on the spatial domain and take some efficient or adaptive feedback methods and obtain gain on feedback information and systematic function.
U.S. Motorola Inc. has delivered motion R1-072701 in the 49bis time meeting of the 3GPP TSG RAN1 that holds in the Orlando of the U.S. 25-29 day in June, 2007, " the associating feedback scheme (Jointfeedback for E-UTRA downlink precoding and CQI) that is used for the indication of downlink precoding and channel quality among the E-UTRA " by name, this motion has proposed the feedback scheme of a kind of CQI and PMI associating, thereby with reducing the feedback quantity that the identical method of CQI feedback quantity reduces PMI.In addition, the call number of one group of Resource Block (RBG) can be used to refer to the report of CQI and PMI simultaneously.This motion has mainly proposed after PMI and the CQI associating, original bitmap feedback scheme, best CQI count feedback scheme and mix feedback scheme report CQI and PMI information in the employing CQI feedback, do not consider the correlation of adjacent channel and compressibility and the channel coherence spatially on the sign indicating number territory, it is not enough to some extent with the effect of the availability of frequency spectrum of raising up link therefore to reduce the PMI feedback quantity.
In addition, American I nterDigital company has delivered motion R1-072782 in the 49bis time meeting of the 3GPP TSG RAN1 that holds in the Orlando of the U.S. 25-29 day in June, 2007, " the binary system difference feedback scheme (Binary Differential Feedback for Downlink MIMOConstant Modulus Pre-coding for E-UTRA) that is used for the precoding of descending MIMO norm among the E-UTRA " by name.This motion has proposed a kind of on time-domain, between the call number of feedback initialization or norm Householder (CM-HH) pre-coding matrix that resets or DFT pre-coding matrix, follow the tracks of and upgrade pre-coding matrix by regularly feeding back a binary system difference information.But this motion do not consider channel in the spatial domain, frequency domain characteristic, promptly underuse the correlation of channel on spatial domain and frequency domain, therefore it is not enough to some extent with the effect of the availability of frequency spectrum of further raising up link to reduce the PMI feedback quantity.Therefore, be necessary to seek the information feedback method that reduces feedback quantity of pre-coding matrix index number in a kind of up link, make full use of the rule that channel embodies and design efficient and simple information feedback method on spatial domain and frequency domain, with the aerial expense of the code book index number (PMI) of the precoding that reduces based on feedback link, thus the purpose that reaches the availability of frequency spectrum that improves up link, the power of saving subscriber equipment and improve the wireless area performance.
Summary of the invention
The objective of the invention is to overcome deficiency of the prior art, the information feedback method that reduces feedback quantity of pre-coding matrix index number in a kind of up link is provided, in the pre-coding matrix index number of the whole bandwidth of feedback, the pre-coding matrix index number of feedback selecteed subband in the CQI feedback system is chosen, sequence number with this subband, the channel quality indication (CQI) information of this subband feeds back to the base station together, thereby by selectively feeding back the pre-coding matrix index number of subband, and the method that repeats to feed back of saving subband index number, significantly reduced the feedback quantity of pre-coding matrix index number.
In one aspect of the invention, proposed a kind of method that reduces feedback quantity of pre-coding matrix index number, comprise step: subscriber equipment is divided into subband with whole bandwidth; Subscriber devices compute goes out the channel quality indication (CQI) information of each subband; Subscriber equipment is according to the subband of the channel quality indication (CQI) information selection needs based on feedback link information of each subband, and described link information comprises sequence number, channel quality indication (CQI) information and the pre-coding matrix index number information of subband; At channel is under the situation of frequency-selective channel, from the pre-coding matrix index number of subscriber equipment to the subband of the pre-coding matrix index number of the whole bandwidth of base station feedback and selected feedback information; And be under the situation of non-frequency-selective channel at channel, subscriber equipment is to the pre-coding matrix index number of whole bandwidth, and the pre-coding matrix index number of the subband of selected feedback information compresses, and the feedback information after will compressing is to the base station.
According to embodiments of the invention, described subscriber equipment selects the step of the subband of needs based on feedback link information to comprise according to the channel quality indication (CQI) information of each subband: according to the feedback system of channel quality indication (CQI) information, the subband conduct that the value of selective channel quality indication (CQI) information is bigger needs the subband of based on feedback link information.
According to embodiments of the invention, the feedback system of described channel quality indication (CQI) information is by the base station decision and send to subscriber equipment.
According to embodiments of the invention, this method also comprises step: scheduling of resource and transmitter optimization are carried out according to described feedack in the base station.
According to embodiments of the invention, described compression is based on the compression of difference, and the information after the described compression comprises: the pre-coding matrix index number of whole bandwidth, and the difference of the pre-coding matrix index number of the pre-coding matrix index number of the subband of selected feedback information and whole bandwidth.
According to embodiments of the invention, described compression is based on the compression of haar wavelet transform, information after the described compression comprises: the pre-coding matrix index number of whole bandwidth, and the pre-coding matrix index number of the subband of selected feedback information carries out the compression result based on haar wavelet transform.
According to embodiments of the invention, the base station is for the subband that does not feed back described link information, and the channel quality indication (CQI) information of whole bandwidth and pre-coding matrix index number are carried out scheduling of resource and transmitter optimization as the channel quality indication (CQI) information and the pre-coding matrix index number of described subband.
According to embodiments of the invention, the judgement of the frequency selectivity of channel in the base station or subscriber equipment carry out.
According to embodiments of the invention, judge by channel condition information whether channel is frequency selectivity.
According to a further aspect in the invention, proposed a kind of subscriber equipment, having comprised: the bandwidth classification apparatus is used for whole bandwidth is divided into subband; The channel quality indication (CQI) information calculation element, be used to calculate the channel quality indication (CQI) information of each subband, and select the subband of needs based on feedback link information according to the channel quality indication (CQI) information of each subband, described link information comprises sequence number, channel quality indication (CQI) information and the pre-coding matrix index number information of subband; And information feedback device, at channel is under the situation of frequency-selective channel, pre-coding matrix index number to the subband of the pre-coding matrix index number of the whole bandwidth of base station feedback and selected feedback information, at channel is under the situation of non-frequency-selective channel, pre-coding matrix index number to whole bandwidth, and the pre-coding matrix index number of the subband of selected feedback information compresses, and the feedback information after will compressing is to the base station.
According to embodiments of the invention, the channel quality indication (CQI) information calculation element is according to the feedback system of channel quality indication (CQI) information, and the subband conduct that the value of selective channel quality indication (CQI) information is bigger needs the subband of based on feedback link information.
According to embodiments of the invention, the feedback system of described channel quality indication (CQI) information is by the base station decision and send to subscriber equipment.
According to embodiments of the invention, the compression that described information feedback device is carried out is based on the compression of difference, and the information after the described compression comprises: the pre-coding matrix index number of whole bandwidth, and the difference of the pre-coding matrix index number of the pre-coding matrix index number of the subband of selected feedback information and whole bandwidth.
According to embodiments of the invention, the compression that described information feedback device is carried out is based on the compression of haar wavelet transform, information after the described compression comprises: the pre-coding matrix index number of whole bandwidth, and the pre-coding matrix index number of the subband of selected feedback information carries out the compression result based on haar wavelet transform.
According to embodiments of the invention, described subscriber equipment also comprises: the selectivity of channel frequency judgment means is used for judging according to channel condition information whether channel is frequency selectivity.
According to embodiments of the invention, the frequency selectivity of described channel is by the base station judgement and send to subscriber equipment.
The present invention also provides a kind of communication system, comprises aforesaid subscriber equipment.
Utilize said method of the present invention and structure and since consider channel in the spatial domain, frequency domain characteristic, make full use of the correlation of channel on spatial domain and frequency domain, reduced the effect of PMI feedback quantity with the availability of frequency spectrum of further raising up link.In addition, for the non-selective channel of frequency, by methods such as difference or Ha Er (Haar) wavelet transformations, the call number of pre-coding matrix of the subband of feedback is further compressed, on the basis that guarantees the radio cells quality, reduce the amount of information of pre-coding matrix index number feedback information.
Description of drawings
Fig. 1 is the schematic diagram of the best pre-coding matrix index number feedback system judgement of wireless area;
Fig. 2 A is the schematic diagram of feedback information mode;
Fig. 2 B is the functional block diagram of MIMO receiver as shown in Figure 1;
Fig. 3 is the mapping schematic diagram of call number and locus in the structuring code book;
Fig. 4 is according to the flow chart that reduces the information feedback method of feedback quantity of pre-coding matrix index number in the up link of the embodiment of the invention;
Fig. 5 is the schematic diagram that the PMI of each subband under the frequency-selective channel changes;
Fig. 6 is the schematic diagram that the PMI of each subband under the non-selective channel of frequency changes;
Fig. 7 is based on the schematic diagram of Best-M algorithm feedback CQI;
Fig. 8 is the differential feedback schematic diagram of the PMI of the non-selective channel of Best-M algorithm lower frequency;
Fig. 9 is based on the schematic diagram of hierarchical algorithm feedback CQI;
Figure 10 is the differential feedback schematic diagram of the PMI of the non-selective channel of hierarchical algorithm lower frequency.
Embodiment
Followingly the specific embodiment of the present invention is described in detail with reference to accompanying drawing.In the following description, ignored some, obscured to prevent that the understanding of the present invention from causing to the incoherent details of method and system of the present invention.
Fig. 1 is the schematic diagram of the best pre-coding matrix index number feedback system judgement of wireless area.According to embodiments of the invention, the present invention adopts the mode of the interior base station (BS) of a wireless area and a plurality of subscriber equipment (UE), different UE adopts different MIMO modes, it can be Single User MIMO (SU-MIMO) mode, also can be multiuser MIMO (MU-MIMO) mode, the information feedback principle figure of MIMO mode as shown in Figure 2.
As shown in Figure 1, base station or UE judge whether current channel is frequency selectivity, if frequency selectivity, then UE is by up link, with the mode of Best-M or layer mode the PMI of the subband of the PMI of whole bandwidth and selected feedback information directly fed back to the base station.If current channel is not a frequency selectivity, then user equipment (UE) compresses the PMI of the subband of the PMI of whole bandwidth and selected feedback information, gives the base station with the PMI feedback information after the compression.
Fig. 2 A is the schematic diagram of feedback information mode.As shown in Figure 2, the base station according to embodiment of the present invention comprises chnnel coding unit 11A-11D, modulating unit 12A-12D, code word map unit 13, precoding unit 14, OFDM map unit 15A-15D and ofdm signal generator 16A-16D etc.User equipment (UE) according to embodiment of the present invention comprises FFT unit 28A-28D, MIMO receiver 20, demodulating unit 26A-26D and channel decoding unit 27A-27D etc.As can be seen from Figure 2, comprise CQI, order and pre-coding matrix index number from MIMO receiver institute feedack, and main purpose of the present invention just is to reduce the feedback quantity of pre-coding matrix index number.
In addition, the chnnel coding unit among Fig. 2, modulating unit, code word map unit and precoding unit have constituted the Frequency Distribution and the scheduling of resource unit 10 of base station together.
Fig. 2 B shows the structured flowchart of the MIMO receiver shown in Fig. 2 A.Shown in Fig. 2 B, MIMO receiver 20 comprises selectivity of channel frequency judging unit 21, it according to outside input obtain pilot frequency information judge current channel be frequency selectivity also be non-frequency selectivity; Bandwidth dividing unit 22, it utilizes the bandwidth information of outside input that whole bandwidth is divided into subband, for example is divided into the subband that is used for the Best-M feedback system, perhaps whole bandwidth is carried out the division of subband on different levels, to be used for the layering feedback system; CQI computing unit 23, it for example calculates the CQI of this subband according to the SNR of subband; PMI computing unit 24, it is used for calculating the PMI of whole each subband of bandwidth, and perhaps each layer gone up the PMI of each subband; Feedback information unit 25, it is under the situation of frequency selectivity at channel, with the best pre-coding matrix index number of selected subband best pre-coding matrix index number together with whole bandwidth, in information such as feedback sub-band serial number and CQI, feed back to the base station together, on the other hand, it is not under the situation of frequency selective channel at channel, best pre-coding matrix index number to selected subband compresses, then in the best pre-coding matrix index number of the whole bandwidth of feedback, the difference of the best pre-coding matrix index number of the best pre-coding matrix index number of each selecteed subband and whole bandwidth is fed back to the base station.In addition, feedback information unit 25 feeds back to the base station after the best pre-coding matrix index number of the best pre-coding matrix index number of selecteed subband and whole bandwidth can also being carried out the Harr conversion together.
Fig. 3 is the mapping schematic diagram of call number and locus in the structuring code book.As shown in Figure 3, for a structurized code book, the pairing pre-coding matrix of its each call number is on being mapped to the space time, also is that the order along with call number presents uniform sequential arrangement.As shown in Figure 3, two adjacent call number positions spatially also are adjacent.
Fig. 4 is according to the flow chart that reduces the information feedback method of feedback quantity of pre-coding matrix index number in the up link of the embodiment of the invention.
As shown in Figure 4, at step S110, UE reports separately movement velocity to the base station, and the base station determines its open loop and closed-loop fashion according to the movement velocity of UE, and the UE that movement velocity is high adopts the open loop MIMO mode, and the UE that movement velocity is low adopts the closed-loop MIMO mode.
At step S111, as mentioned above, the bandwidth dividing unit 22 of UE is divided into several subbands with whole bandwidth, and each subband comprises several Resource Block.The CQI computing unit 23 of UE calculates the CQI of own each subband, select the CQI performance good, be that the big subband of CQI value is as the subband that needs feedback information, for example select preceding M maximum subband of CQI value, perhaps select the subband of CQI value greater than pre-set threshold, concrete selection mode is informed UE after being determined by the base station.
At step S112, the PMI computing unit 24 of UE calculates the best pre-coding matrix index number of own each subband, and the best pre-coding matrix index number of whole bandwidth.
At step S113, selectivity of channel frequency computing unit 25 judges according to channel condition information whether channel is frequency selectivity.
At step S114, if channel is a frequency-selective channel, the best pre-coding matrix index number of each subband changes obviously, then the best pre-coding matrix index number of selecteed subband also can have nothing in common with each other, the feedback information unit 25 of UE is with the best pre-coding matrix index number of the selecteed subband best pre-coding matrix index number together with whole bandwidth, in the feedback sub-band serial number, in the time of other relevant informations such as CQI, feed back to the base station together, thereby avoided the feedback that repeats of sub-band serial number, the PMI that selectively feeds back subband simultaneously also can save the feedack amount greatly.
At step S115, if the channel non-selective channel that is frequency, the best pre-coding matrix index number of each subband changes not obvious, then the best pre-coding matrix index number of selecteed subband also can be same or similar, thereby can utilize this specific character, before the base station feedback sub-band information, the best pre-coding matrix index number of the 25 pairs of selecteed subbands in feedback information unit further compresses, thereby under the prerequisite of sacrificing less feedback accuracy, further reduce the feedack amount.
Under the situation of the non-selective channel of frequency, the feedback information unit 25 of UE is in the best pre-coding matrix index number of the whole bandwidth of feedback, feed back the difference of the best pre-coding matrix index number of the best pre-coding matrix index number of each selecteed subband and whole bandwidth, thereby reduce call number feedack amount.
Under the situation of the non-selective channel of frequency, the feedback information unit 25 of UE also can carry out the Haar conversion together with the best pre-coding matrix index number of selecteed subband and the best pre-coding matrix index number of whole bandwidth.
At step S116, the PMI feedback information after feedback information unit 25 will compress is to the base station, thus minimizing call number feedack amount.
At step S117, aspect the base station, the CQI and the PMI information of the selecteed subband that feeds back up according to subscriber equipment, and the information of whole bandwidth is carried out scheduling of resource and transmitter optimization.For the subband that is not fed information, the CQI of whole bandwidth and PMI are carried out scheduling of resource and transmitter optimization as the CQI and the PMI of this subband.
Next, whether judge current sub-district still in work at step S118, if the result who judges is sure, then flow process forwards step S111 to, continues above-mentioned operation, if the result who judges negates then to finish.Like this, to (6), ensure that the base station of wireless area and all subscriber equipmenies normally move by circulation execution in step (1).
[application example one]
(1) structure of wireless area
As shown in Figure 1, should adopt the mode of a base station (BS) and a plurality of subscriber equipment (UE) in the wireless area with example, different UE adopts different MIMO modes, can be the SU-MIMO mode, also can be the MU-MIMO mode, the information feedback principle figure of MIMO mode as shown in Figure 2.
(2) structure of precoder code book in the closed-loop MIMO system
For a structurized code book, the pairing pre-coding matrix of its each call number is on being mapped to the space time, also is that the order along with call number presents uniform sequential arrangement, and as shown in Figure 3, two adjacent call number positions spatially also are adjacent.
(3) bandwidth dividing unit 22 of UE is divided into several subbands with whole bandwidth, and each subband comprises several Resource Block.UE calculates the CQI of own each subband, selects the CQI performance best, i.e. M maximum subband conduct of CQI value needs the subband of feedback information.
(4) the CQI computing unit of UE calculates the best pre-coding matrix index number of own each subband, and the best pre-coding matrix index number of whole bandwidth.And take the feedback system of different PMI according to the frequency selective characteristic of channel, specifically as shown in Figure 4.The size of pre-coding matrix index number is decided by code book (Codebook) size of the precoder of transmitter: the code book that 3 bits are represented, then the maximum of PMI value Q is 2
3The code book that 4 bits are represented, then the maximum of PMI value is 2
4If the code book that 5 bits are represented, then the maximum of PMI value is 2
5
If channel is a frequency-selective channel, because between each subband is incoherent on frequency domain, on the spatial domain, also can there be certain incoherence, be that the space selective fading experienced between the adjacent sub-bands is different, the best pre-coding matrix index number of each subband changes can be apparent in view, the best pre-coding matrix index number of then selecteed M subband also can have nothing in common with each other, as shown in Figure 5.
If the channel non-selective channel that is frequency, owing on frequency domain, be concerned with between each subband, on the spatial domain, also be concerned with to a certain extent, be that the space selective fading experienced between the adjacent sub-bands is same or similar, the variation of the best pre-coding matrix index number of each subband is not obvious, and the best pre-coding matrix index number of then selecteed M subband also can be same or similar.As shown in Figure 6.
(5) for frequency-selective channel, because the PMI of a selecteed M subband has nothing in common with each other, the feedback information unit 25 of UE is in the CQI and subband index information of the best subband of a base station feedback M CQI, the PMI of this M subband is fed back to the base station together, simultaneously UE is also to the average CQI of the whole bandwidth of base station feedback, with the PMI of whole bandwidth, as shown in Figure 7.
(6) for the non-selective channel of frequency, because the PMI of a selecteed M subband is same or similar, thereby can utilize this same or similar, to sacrifice less precision is cost, after feedback information unit 25 will need the PMI of M subband feeding back further to compress again to base station feedback, thereby further reduce the feedack amount.
Under the situation of the non-selective channel of frequency, the feedback information unit 25 of UE can feed back the difference of the PMI of the PMI of the best subband of a selecteed M CQI and whole bandwidth in the PMI of the whole bandwidth of feedback.If the code book that 3 bits are represented, then the maximum of PMI value is 2
3Because under the situation of the non-selective channel of frequency, the PMI of each subband is same or similar, the difference of the PMI of then selecteed M subband and the PMI of whole bandwidth can be represented with 1bit.The PMI of feedback 0 this subband of expression is-1 with respect to the increment of the PMI of whole bandwidth, and the PMI of feedback 1 this subband of expression is+1 with respect to the increment of the PMI of whole bandwidth, and it is identical with the PMI of whole bandwidth not feed back the PMI that then represents this subband.
With M=4 is example,
If adopt the mode of difference, as Fig. 8, reduce feedback quantity by the mode of sacrificing feedback accuracy, at first feed back the PMI of whole bandwidth, feed back the PMI of the best M of a selecteed CQI subband and the difference between the whole bandwidth PMI again.
Under the situation of the non-selective channel of frequency, feedback information unit 25 also can adopt the mode based on the Haar compression, feed back to the base station after the PMI of the subband that the PMI of whole bandwidth and M the CQI that need be fed is best further compresses together, thereby reach the purpose of further minimizing feedback information volume.
With M=4 is example,
y＝[PMI
1?PMI
2?PMI
3?0?PMI
4?0?PMI
wb?0]
PMI
1, PMI
2, PMI
3, PMI
4, be respectively the PMI of the best subband of a selecteed M CQI.PMI
WbBe the PMI of whole bandwidth.
y
3＝yW
8
For the y after the conversion
3, element y
3[0] because the amount of information maximum that comprises need be represented element y with 3 bits
3[5], y
3[6], y
3[7] information is incoherent for conversion, can directly ignore element y
3[4] amount of information that comprises is less relatively, can represent element y with 1 bit
3[1], y
3[2] and y
3[3] then represent with 2 bits.
After feedback information is received in the base station, pass through y=y
3F recovers the PMI information of feedback.
The supposing the system bandwidth is 10MHz, altogether 50 RB.If each subband is made of 5 RB, adopt the feedback system of Best-M, the M value is taken as 4, each PMI value is represented with 3bits, the mean P MI feedback quantity of whole bandwidth is represented with 3bits, from table 1, can find, under the non-selective channel circumstance of frequency, employing is based on the feedback method of the PMI of PMI that feeds back whole bandwidth and selecteed subband, call number feedback method by further difference or Haar compression can reduce feedback quantity greatly, improves feedback efficiency, thereby save the frequency spectrum resource of the preciousness of up link, save the power of battery of UE.
(7) scheduling of resource and transmitter optimization are carried out according to feedback information in the base station
The CQI and the PMI information of M the subband of CQI the best that feed back up according to UE the base station, and the CQI of whole bandwidth and PMI information are carried out scheduling of resource and transmitter optimization.For the subband that does not have feedback information, the base station is carried out scheduling of resource and transmitter optimization with the CQI and the PMI information of whole bandwidth as the CQI and the PMI information of this subband.
Table 1 has provided the comparison of the total bit number of PMI that the PMI feedback method of using this example and the method for not using this example feed back.As can be seen from Table 1, utilize the method for this example, can significantly reduce the PMI bit number that will feed back.
Table 1
[application example two]
(1) structure of wireless area
As shown in Figure 1, should adopt the mode of a base station (BS) and a plurality of subscriber equipment (UE) in the wireless area with example, different UE adopts different MIMO modes, can be the SU-MIMO mode, also can be the MU-MIMO mode, the information feedback principle figure of MIMO mode as shown in Figure 2.
(2) structure of precoder code book in the closed-loop MIMO system
For a structurized code book, the pairing pre-coding matrix of its each call number is on being mapped to the space time, also is that the order along with call number presents uniform sequential arrangement, and as shown in Figure 3, two adjacent call number positions spatially also are adjacent.
(3) bandwidth dividing unit 22 of UE is spreaded entire belt and is split into several layers, is set at the layer of different stage according to the size of subband bandwidth on the whole bandwidth, and the subband bandwidth is big more, and promptly the number of sub-bands that each layer comprised is few more, and pairing layer is low more.The bottom has only a subband, is whole bandwidth.Subband on the bandwidth of high one deck be will low one deck each subband further be divided into 2 to 3 boys with constitute, the rest may be inferred, up to each subband of this layer be feedback CQI based on least unit till.The CQI computing unit 23 of UE calculates the CQI that each layer gone up each subband, and the subband that every layer of CQI performance is best is as the subband that needs feedback information, as shown in Figure 9.
(4) the PMI computing unit 24 of UE calculates the PMI that each layer gone up each subband, comprises the PMI of whole bandwidth.And take the feedback system of different PMI according to the frequency selective characteristic of channel, specifically as shown in Figure 4.The size of pre-coding matrix index number is decided by code book (Codebook) size of the precoder of transmitter: the code book that 3 bits are represented, then the maximum of PMI value Q is 2
3The code book that 4 bits are represented, then the maximum of PMI value is 2
4If the code book that 5 bits are represented, then the maximum of PMI value is 2
5
If channel is a frequency-selective channel, because between each subband is incoherent on frequency domain, on the spatial domain, also can there be certain incoherence, be that the space selective fading experienced between the adjacent sub-bands is different, the PMI of each subband changes can be apparent in view, then the PMI of selecteed subband also can have nothing in common with each other on each layer, as shown in Figure 5.
If the channel non-selective channel that is frequency, owing on frequency domain, be concerned with between each subband, on the spatial domain, also be concerned with to a certain extent, be that the space selective fading experienced between the adjacent sub-bands is same or similar, the variation of the PMI of each subband is not obvious, and then the PMI of selecteed subband also can be same or similar on each layer.As shown in Figure 6.
(5) for frequency-selective channel, because the PMI of the selecteed subband of each layer has nothing in common with each other, the feedback information unit 25 of UE is in the CQI and subband index information of the best subband of each floor CQI of base station feedback, the PMI of these subbands is fed back to the base station together, UE is also to the average CQI of the whole bandwidth of base station feedback and the PMI of whole bandwidth simultaneously.
(6) for the non-selective channel of frequency, because the PMI of every layer of selecteed subband is same or similar, thereby can utilize this same or similar, to sacrifice less precision is cost, after feedback information unit 25 needs the PMI of feedback subband further to compress each layer again to base station feedback, thereby further reduce the feedack amount.
Under the situation of the non-selective channel of frequency, UE can promptly the PMI of the bottom time, feed back the PMI of the best subband of the selecteed CQI of other each layers and the difference of whole bandwidth PMI at the PMI of the whole bandwidth of feedback, promptly with the difference of the PMI of the bottom.If the code book that 3 bits are represented, then the maximum of PMI value is 2
3Because under the situation of the non-selective channel of frequency, the PMI of each subband is same or similar, then the difference of the PMI of the PMI of selecteed subband and whole bandwidth can be represented with 1bit.The PMI of feedback 0 this subband of expression is-1 with respect to the increment of the PMI of whole bandwidth, and the PMI of feedback 1 this subband of expression is+1 with respect to the increment of the PMI of whole bandwidth, and it is identical with the PMI of whole bandwidth not feed back the PMI that then represents this subband.
Equaling 4 with hierachy number is example,
If adopt the mode of difference, as Figure 10, reduce feedback quantity by the mode of sacrificing feedback accuracy, at first feed back the subband of the bottom, i.e. the PMI of whole bandwidth.Then in the PMI of the best subband of the feedback second layer selecteed CQI, only feed back the difference between the PMI of the PMI of this subband and the whole bandwidth of bottom.The rest may be inferred, up in the PMI of the 4th layer of subband that selecteed CQI is best of feedback, only feeds back the difference between the PMI of the PMI of this subband and the whole bandwidth of bottom.
Under the situation of the non-selective channel of frequency, UE also can adopt the mode based on Haar compression, and the PMI of the subband that each layer CQI is best has comprised the PMI of whole bandwidth, feed back to the base station after further compressing, thereby reach the purpose of further minimizing feedback information volume.
Equaling 4 with hierachy number is example,
y＝[PMI
1?0?PMI
2?0?PMI
3?0?PMI
4?0]
PMI
1, PMI
2, PMI
3And PMI
4, be respectively the PMI of four layers of selecteed best subband.
y
3＝yW
8
For the y after the conversion
3, element y
3[0] because the amount of information maximum that comprises need be represented element y with 3 bits
3[4], y
3[5], y
3[6], y
3[7] information is incoherent for conversion, can directly ignore element y
3[2], y
3[3] amount of information that comprises is relatively very little, can represent element y with 1 bit
3[1] then represents with 2 bits.
After feedback information is received in the base station, pass through y=y
3F recovers the PMI information of feedback.
The supposing the system bandwidth is 10MHz, altogether 50 RB.Then the whole bandwidth of the second layer is divided into 3 subbands, and the RB number that each subband comprises is 17,16 and 17.Each subband of the second layer further is divided into two, constitute the 3rd layer, wherein first subband of the second layer is divided into a subband that comprises 9 RB at the 3rd layer, with a subband that comprises 8 RB, second subband of the second layer is divided into two subbands that comprise 8 RB at the 3rd layer, and the 3rd subband of the second layer is divided into a subband and a subband that comprises 9 RB that comprises 8 RB at the 3rd layer.At the 4th layer, each subband of the 3rd layer is continued to be divided into two at last, be divided into 12 subbands altogether.First and the 12 subband comprise 5 RB, and all the other ten subbands comprise 4 RB.Each PMI value is represented with 3bits, the mean P MI feedback quantity of whole bandwidth is represented with 3bits, from table 2, can find, under the non-selective channel circumstance of frequency, adopt feedback method, by the call number feedback method of further difference or Haar compression based on the PMI of PMI that feeds back whole bandwidth and selecteed subband, can reduce feedback quantity greatly, improve feedback efficiency, thereby save the frequency spectrum resource of the preciousness of up link, the power of battery of saving UE.
(7) scheduling of resource and transmitter optimization are carried out according to feedback information in the base station
The CQI and the PMI information of M the subband of CQI the best that feed back up according to UE the base station, and the CQI of whole bandwidth and PMI information are carried out scheduling of resource and transmitter optimization.For the subband that does not have feedback information, the base station with the subband of this subband at the low layer place be fed CQI and PMI information as the CQI and the PMI information of this subband, if this subband does not have feedback information at the subband at low layer place yet, then seek the subband of this subband under lower one deck, up to searching out the bottom, the CQI of whole bandwidth and PMI information as the CQI and the PMI information of this subband, are carried out scheduling of resource and transmitter optimization.
Table 2 has provided the comparison of the total bit number of PMI that the PMI feedback method of using this example and the method for not using this example feed back.As can be seen from Table 1, utilize the method for this example, can significantly reduce the PMI bit number that will feed back.
Table 2
[modification]
Described above is to judge the MIMO mode according to the speed and the path loss of subscriber equipment by the base station, but this function also can realize by subscriber equipment, and notify judged result to the base station by up link.
In addition, in the above embodiments, in MIMO receiver 20, realized channel frequency judging unit 21.But the function of channel frequency judging unit 21 can realize in base station side, by down link judged result is notified to subscriber equipment then.
As mentioned above, according to the solution of the present invention, at first UE calculates the CQI of own each subband, selects the good subband of CQI performance as the subband that needs feedback information.Secondly UE calculates the best pre-coding matrix index number of own each subband, and the best pre-coding matrix index number of whole bandwidth.If channel is a frequency-selective channel, the best pre-coding matrix index number of each subband changes obviously, and UE feeds back to the base station with the best pre-coding matrix index number of selecteed subband together with the best pre-coding matrix index number of whole bandwidth.If the channel non-selective channel that is frequency, the best pre-coding matrix of each subband changes not obvious, after UE carries out difference or wavelet transformation compression with the best pre-coding matrix index number of selecteed subband, feed back to the base station together with the best pre-coding matrix index number of whole bandwidth.At last, scheduling of resource and transmitter optimization are carried out according to feedback information in the base station.
As seen, the present invention is by feeding back the PMI of selecteed subband based on the feedback system of CQI, and to further reducing feedback quantity of pre-coding matrix index number by modes such as difference or Haar compressed feedback.Therefore, the present invention can be applied respectively according to actual conditions, can be the third generation (3G), super three generations (S3G), the 4th generation (4G) cellular mobile communication and Digital Television, wireless lan (wlan), self-organizing network (Mesh, Ad Hoc, Censor Network), the closed loop feedback scheme of digital home network (e-Home), wireless wide area network systems such as (WWAN) provides important theory foundation and concrete implementation method.
Claims (17)
1, a kind of method that reduces feedback quantity of pre-coding matrix index number comprises step:
Subscriber equipment is divided into subband with whole bandwidth;
Subscriber devices compute goes out the channel quality indication (CQI) information of each subband;
Subscriber equipment is according to the subband of the channel quality indication (CQI) information selection needs based on feedback link information of each subband, and described link information comprises sequence number, channel quality indication (CQI) information and the pre-coding matrix index number information of subband;
At channel is under the situation of frequency-selective channel, from the pre-coding matrix index number of subscriber equipment to the subband of the pre-coding matrix index number of the whole bandwidth of base station feedback and selected feedback information; And
At channel is under the situation of non-frequency-selective channel, and subscriber equipment is to the pre-coding matrix index number of whole bandwidth, and the pre-coding matrix index number of the subband of selected feedback information compresses, and the feedback information after will compressing is to the base station.
2, the method for claim 1, wherein described subscriber equipment selects the step of the subband of needs based on feedback link information to comprise according to the channel quality indication (CQI) information of each subband:
According to the feedback system of channel quality indication (CQI) information, the subband conduct that the value of selective channel quality indication (CQI) information is bigger needs the subband of based on feedback link information.
3, method as claimed in claim 2, wherein, the feedback system of described channel quality indication (CQI) information is by the base station decision and send to subscriber equipment.
4, the method for claim 1 also comprises step:
Scheduling of resource and transmitter optimization are carried out according to described feedack in the base station.
5, the method for claim 1, wherein, described compression is based on the compression of difference, and the information after the described compression comprises: the pre-coding matrix index number of whole bandwidth, and the difference of the pre-coding matrix index number of the pre-coding matrix index number of the subband of selected feedback information and whole bandwidth.
6, method according to claim 1, wherein, described compression is based on the compression of haar wavelet transform, information after the described compression comprises: the pre-coding matrix index number of whole bandwidth, and the pre-coding matrix index number of the subband of selected feedback information carries out the compression result based on haar wavelet transform.
7, method according to claim 1, wherein, the base station is for the subband that does not feed back described link information, and the channel quality indication (CQI) information of whole bandwidth and pre-coding matrix index number are carried out scheduling of resource and transmitter optimization as the channel quality indication (CQI) information and the pre-coding matrix index number of described subband.
8, the method for claim 1, wherein judge by channel condition information whether channel is frequency selectivity.
9, method as claimed in claim 8, wherein the judgement of the frequency selectivity of channel in the base station or subscriber equipment carry out.
10, a kind of subscriber equipment comprises:
The bandwidth classification apparatus is used for whole bandwidth is divided into subband;
The channel quality indication (CQI) information calculation element, be used to calculate the channel quality indication (CQI) information of each subband, and select the subband of needs based on feedback link information according to the channel quality indication (CQI) information of each subband, described link information comprises sequence number, channel quality indication (CQI) information and the pre-coding matrix index number information of subband; And
Information feedback device, at channel is under the situation of frequency-selective channel, pre-coding matrix index number to the subband of the pre-coding matrix index number of the whole bandwidth of base station feedback and selected feedback information, at channel is under the situation of non-frequency-selective channel, pre-coding matrix index number to whole bandwidth, and the pre-coding matrix index number of the subband of selected feedback information compresses, and the feedback information after will compressing is to the base station.
11, subscriber equipment as claimed in claim 10, wherein, the channel quality indication (CQI) information calculation element is according to the feedback system of channel quality indication (CQI) information, and the subband conduct that the value of selective channel quality indication (CQI) information is bigger needs the subband of based on feedback link information.
12, subscriber equipment as claimed in claim 11, wherein, the feedback system of described channel quality indication (CQI) information is by the base station decision and send to subscriber equipment.
13, subscriber equipment as claimed in claim 10, wherein, the compression that described information feedback device is carried out is based on the compression of difference, and the information after the described compression comprises: the pre-coding matrix index number of whole bandwidth, and the difference of the pre-coding matrix index number of the pre-coding matrix index number of the subband of selected feedback information and whole bandwidth.
14, subscriber equipment according to claim 10, wherein, the compression that described information feedback device is carried out is based on the compression of haar wavelet transform, information after the described compression comprises: the pre-coding matrix index number of whole bandwidth, and the pre-coding matrix index number of the subband of selected feedback information carries out the compression result based on haar wavelet transform.
15, subscriber equipment as claimed in claim 10 also comprises:
The selectivity of channel frequency judgment means is used for judging according to channel condition information whether channel is frequency selectivity.
16, subscriber equipment as claimed in claim 10, wherein, the frequency selectivity of described channel is judged by the base station and is sent to subscriber equipment.
17, a kind of communication system comprises subscriber equipment as claimed in claim 10.
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Application publication date: 20090401 |