CN103095401B - The method and apparatus of information feedback - Google Patents

Abstract

Present invention relates in general to the method and apparatus for the information feedback in radio communication.According to the embodiment of the present invention, propose a kind of dual stage feedback mechanism, in making every grade, transmit dissimilar channel feedback.Especially, during the first order, feed back the first channel condition information for the reference point in measuring assembly, it is such as with during channel long and/or the relevant absolute CQI of broadband characteristics; During the second level, feed back the second channel state information for each point in measuring assembly, its be such as with channel in short-term and/or the relevant differential CQI of subband feature.Be used to reconstruct the channel condition information of each point in for measuring assembly in the first order and second level feedack in base station.In this way, the feedback overhead be associated with channel condition information can effectively be reduced.Further, in Limited Feedback expense situation, the accuracy of CQI feedback can be improved.Further, both unicast and CoMP transmission can be supported.

Description

Method and device for feeding back channel state information

Technical Field

Embodiments of the present invention relate generally to the field of wireless communications, and more particularly, to a method and apparatus for channel state information feedback in wireless communications.

Background

The Long Term Evolution (LTE)/long term evolution-advanced (LTE-a) standards and systems of the third generation partnership project (3GPP) are considered to be important development directions for wireless communication systems. In the wireless communication system, in order to obtain higher spectrum utilization rate, the system adopts a mode of co-frequency networking, so that User Equipment (UE) positioned at the edge of a cell receives co-frequency interference from an adjacent cell, and the service quality and the throughput of edge users are severely limited. In order to meet the requirements of LTE-a in terms of system capacity, instantaneous peak data rate, spectrum, cell edge user throughput, delay, etc., a coordinated multi-Point (CoMP) technology has been proposed to improve system performance.

The CoMP technology converts interference originally in a neighboring cell into useful information through cooperation of inter-cell base stations based on sharing of Channel State Information (CSI) and data information by each cooperative base station to different degrees. The core idea of CoMP is that when a user equipment is located in a cell border area, it can receive signals from multiple cells (or base stations) simultaneously, while its own transmissions can also be received by multiple cells (or base stations) simultaneously.

CoMP transmission techniques are mainly divided into two cases according to whether a base station shares user data. One is Joint Processing (JP), and the other is coordinated scheduling/Beamforming (CS/CB).

The joint processing is also called "interference utilization", that is, a user is served by a plurality of cooperating base stations together, interference between users is eliminated by the joint processing at the cooperating base stations, and an interference signal is utilized as a useful signal. Cooperative scheduling/beamforming, also referred to as "interference avoidance," provides for users to be served by only a single base station, and reduces collisions in time, frequency, or space of resources used by neighboring cell edge regions by efficiently allocating system resources.

In LTE/LTE-a systems, CoMP transmission can be effectively used to reduce inter-cell interference (ICI) and improve coverage area for data rates, cell-edge throughput, and/or improve overall system throughput. It is known that CoMP transmission, in particular joint CoMP transmission, requires a large amount of channel state information, CSI, feedback from each UE for centralized scheduling and centralized precoding among all cooperating base stations (also referred to as enodebs or enbs in 3 GPP).

In 3gpp ran1, an important issue for the new work item for CoMP is whether the definition of Channel Quality Identification (CQI) feedback should be modified for FDD downlink CoMP. The CQI feedback depends on several parameters including, but not limited to, RI (rank indicator), PMI (precoding matrix indicator) and the transmission mode of PDSCH in the assumed CQI reference resource. It is not clear whether a new PDSCH transmission mode is to be introduced for CoMP at present, but in any case the UE derived CQI value will depend on its assumption about single point transmission or CoMP transmission (whether CS/CS or JP).

It is not realistic to expect the UE to feed back a large number of CQI values, each corresponding to a different combination of these assumed parameters. Since this would imply a very considerable CQI computation complexity on the UE side as well as uplink feedback overhead.

Moreover, any mismatch between the assumed parameters on the UE side and the actual parameters eventually used by the eNB side may also affect the applicability of the reported CQI.

Nevertheless, without modifying the CQI definition of release 10(Rel-10), it is possible for the eNB to adjust the received CQI feedback to match the actual transmission mode in some open loop adaptive manner. However, the interference uncertainty in the real world also makes it difficult to get an accurate CQI.

Furthermore, to obtain attractive performance gains from CoMP, it is possible to dynamically switch between single point transmission and CoMP. Therefore, this requires that the CQI feedback design should allow the eNB to be able to reconstruct single-point CQI and multi-point CQI.

Disclosure of Invention

Based on the above situation, it is desirable to further reduce the feedback overhead of the channel state information. Further, it is desirable that the accuracy of CQI feedback can be improved with limited feedback overhead. Still further, it is desirable that the CQI feedback mechanism be able to support both single point transmission and CoMP transmission.

To achieve one or more of the above objects, embodiments of the present invention provide a method and apparatus for feeding back channel state information in a wireless communication system.

In a first aspect of the present invention, a method for feeding back channel state information in a user equipment is provided, including: feeding back first channel state information for a reference point in a measurement set during a first period; and feeding back second channel state information for each point in the measurement set during a second time period.

In the embodiment of the present invention, the first channel state information includes an absolute channel quality indicator CQI of the reference point; and the second channel state information comprises differential channel quality identities, CQIs, for respective points in the measurement set. Further, the differential CQI may be differentially encoded with respect to an absolute CQI of the reference point or with respect to an absolute CQI of the respective point.

In a second aspect of the present invention, there is provided a method of acquiring channel state information at a base station, comprising: receiving first channel state information for a reference point in a measurement set; receiving second channel state information for each point in the measurement set; and reconstructing channel state information for each point in the measurement set based on the first and second channel state information. In an embodiment of the present invention, the base station is any one of: a serving base station, a primary transmission base station, a base station with the best channel quality, or a base station with high computing power.

In a third aspect of the present invention, an apparatus for feeding back channel state information in a user equipment is provided, including: first feedback means configured to feedback, during a first period, first channel state information for a reference point in a measurement set; and second feedback means configured to feed back second channel state information for each point in the measurement set during a second time period.

In a fourth aspect of the present invention, an apparatus for acquiring channel state information at a base station is provided, including: first receiving means configured to receive first channel state information for a reference point in a measurement set; second receiving means configured to receive second channel state information for each point in the measurement set; and reconstructing means configured to reconstruct the channel state information for each point in the measurement set based on the first channel state information and the second channel state information.

Drawings

The above and other objects, features and advantages of embodiments of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. In the accompanying drawings, which illustrate by way of example, but not by way of limitation, several possible embodiments of the invention

Figure 1 illustrates an example diagram of a wireless communication system using CoMP transmission;

fig. 2 illustrates generally a channel state information feedback principle according to an exemplary embodiment of the present invention;

fig. 3 schematically shows a flowchart of a method 300 of feeding back channel state information in a user equipment according to an exemplary embodiment of the present invention;

fig. 4 schematically illustrates a flow chart of a method 400 of acquiring channel state information at a base station according to an exemplary embodiment of the invention;

fig. 5 schematically shows a block diagram of an apparatus 500 for feeding back channel state information in a user equipment according to an exemplary embodiment of the present invention; and

fig. 6 schematically shows a block diagram of an apparatus 600 for acquiring channel state information at a base station according to an exemplary embodiment of the present invention.

In the drawings, the same or corresponding reference numerals are used to denote the same or corresponding contents or portions.

Detailed Description

Embodiments of the present invention are described in detail below with reference to the accompanying drawings. Referring initially to fig. 1, an exemplary diagram of a wireless communication system 100 using CoMP transmission is shown.

As shown in fig. 1, three base stations (enbs) and two User Equipments (UEs) are exemplarily shown. In the system 100 using CoMP transmission, when the user equipment UE is at the cell edge, multiple points (i.e., the base station eNB1, eNB2, and eNB3) share the channel state information and the data information to different degrees, thereby converting the interference that is originally a neighboring cell into useful information through cooperation of inter-cell base stations.

Although only a point (point) in the form of a base station eNB is shown in fig. 1, it may also be a radio remote RRH of the base station. These referred points are collectively referred to herein as a measurement set. Generally, the UE needs to measure the reference signal of each point in the measurement set to derive the channel state information.

Fig. 2 illustrates generally the channel state information feedback principle according to an exemplary embodiment of the present invention.

As shown in fig. 2, the core ideas of the embodiments of the present invention are: in a wireless communication system, channel state information feedback of a UE is divided into two stages (stages), and different channel state information is fed back in each stage. More specifically, during the first stage 201 or first period, first channel state information for a reference point in the measurement set is fed back; during the second stage 202, or second time period, second channel state information for each point in the measurement set is fed back. The first channel state information may be an absolute CQI and the second channel state information may be a differential CQI. In some embodiments, the absolute CQI may be a wideband and/or long-term (long-term) CQI, and the differential CQI may be a sub-band and/or short-term (short-term) CQI.

It should be noted that the arrows shown in fig. 2 only represent the relationship of the data to the points in the measurement set and do not represent the actual direction of transmission. In the first stage, only the first channel state information may be transmitted to a specified point in the measurement set, i.e. only one absolute CQI may be transmitted. In the second stage, the differential CQI given to each point in the measurement set may be fed back to it separately. Optionally, in the second stage, the second channel state information, i.e. M differential CQIs, may still be transmitted only to the specified point, where M is the number of points in the measurement set.

As known to those skilled in the art, CQI reporting may be periodic or aperiodic. Therefore, the first-stage feedback and the second-stage feedback can be repeated periodically or started based on event triggering. When repeated periodically, the periods of both may be the same or different. The information fed back at the first and second stages is used at the base station to reconstruct the CQI for each point in the measurement set. In this way, feedback overhead related to channel state information can be effectively reduced.

Note that in the following description, the terms "stage" and "period" are used interchangeably, both of which refer to a time interval for transmitting information.

Referring to fig. 3, a flow chart of a method 300 of feeding back channel state information in a user equipment according to an exemplary embodiment of the present invention is schematically shown. Note that according to an embodiment of the present invention, at least one User Equipment (UE) is typically included in the wireless communication system concerned. The method 300 may be performed at each of these UEs, e.g., by the UE itself or components thereof.

After the method 300 starts, at step S301, the UE feeds back first channel state information for a reference point in a measurement set during a first period.

According to an embodiment of the present invention, the first channel state information may include an absolute CQI of a channel between the UE and a reference point in the measurement set. The absolute CQI may be a wideband and/or a long-term CQI. Or in other words, the first channel state information may primarily relate to cell-specific channel information. This definition of absolute CQI may re-use the definition of single point CQI of Rel-10 to obtain the channel quality from the reference point to the UE.

The long term wideband CQI varies based on the specific implementation. The following illustrates how the long term wideband CQI is derived. Those skilled in the art will appreciate that the following description is by way of example only, and not by way of limitation, as measured by any suitable technique now known or later developed. The scope of the invention is not limited in the above respects.

The UE may update its long-term wideband CQI for the current subframe, for example, by a weighting of the long-term wideband CQI for the previous subframe and the short-term wideband CQI for the current subframe, which may be expressed as:

${\stackrel{\‾}{\mathrm{CQI}}}_{c_j,j}\left(n\right)=\mathrm{\α}{\stackrel{\‾}{\mathrm{CQI}}}_{c_j,j}(n-1)+(1-\mathrm{\α}){\mathrm{CQI}}_{c_j,j}---\left(1\right)$

in the above formula, the first and second carbon atoms are,denotes from c_jA long-term wideband CQI which is from a point to a jth UE and in an nth subframe (a current subframe);is from the c th_jShort-time wideband CQI at the current subframe from point to jth UE, α is a weighting factor that varies depending on the implementation, c_jIs the number of reference points for the jth UE.

Wherein the short-time wideband CQI, i.eThe calculation can be performed in a number of ways. For example, the following equations (2) or (3) give two alternatives. Note that in equations (2) and (3), the receive beamformer, PMI, and eigen (eigen) channels are wideband.

Mode 1: ${\mathrm{CQI}}_{c_j,j}=\frac{{\left|u_j{H}_{c_j,j}{v}_{c_j,j}\right|}^2}{{\mathrm{\σ}}_o^2}---\left(2\right)$

mode 2: ${\mathrm{CQI}}_{c_j,j}=\frac{{\left|u_j{H}_{c_j,j}{v}_{c_j,j}\right|}^2}{{\mathrm{\σ}}_{f,j}^2}---\left(3\right)$

in the above-mentioned formula,is from the c th_jA channel from a point to a jth UE; u. of_jIs the predicted receive beamformer at the jth UE;is from the jth UE to the c_jFeedback PMI of a point;is noise plus interference outside the CoMP measurement set; andis the noise plus the overall interference of the jth UE.

In approach 1, the short-time wideband CQI for the reference point can be obtained by assuming that the interference is only from outside the CoMP measurement set. In mode 2, the short-time wideband CQI for the reference point can be calculated by considering the total interference power from all other points as interference.

Mode 1 can easily derive CoMP-specific CQI based on PMI feedback and CQI at each point. In addition, mode 1 can also derive CQI for SU-MIMO and MU-MIMO after appropriate compensation. Mode 2 can support SU-MIMO and MU-MIMO well. Further, CoMP-specific CQI may be derived based on PMI feedback and CQI feedback for various points. Thus, mode 1 and mode 2 both provide flexible handover capability between SU-MIMO, MU-MIMO and CoMP.

If the long-time broadband CQI is not reported in the current subframe, the method comprises the following stepsIs the recently reported long term wideband CQI, otherwiseEqual to the most recently updated long term wideband CQI, which will be reported in the current subframe.

According to an embodiment of the invention, the reference point in the measurement set may be any of: a service point, a primary transmission point, a point with the best channel quality, or a point with an intermediate channel quality. Further, the reference point may be selected by the service point or recommended by the UE.

In particular, for the comp cs/CB, the reference point may be a serving point or a main transmission point of the UE. For CoMPJP, the reference point may be the service point of the UE, the point with the best channel quality, or the point with the middle channel quality.

According to embodiments of the present invention, this first channel state information may be transmitted to a designated point in the measurement set. The designated point may be any of: a service point, a primary transmission point, a point with the best channel quality, or a point with high computational power. Further, the specified point may be selected by the service point or recommended by the user device.

The method 300 then proceeds to step S302, where the UE feeds back second channel state information for each point in the measurement set during a second time period.

According to an embodiment of the present invention, the second channel state information may include differential CQI of each point in the measurement set. The differential CQI may indicate a sub-band and/or a short-time CQI. Or in other words, the differential CQI may mainly relate to channel state information related to inter-cell cooperation.

The differential CQI may be differentially encoded in a variety of ways. According to an embodiment of the present invention, the differential CQI may be differentially encoded (hereinafter referred to as "differential scheme one") with respect to an absolute CQI (long-term wideband CQI) of a reference point in the measurement set. According to another embodiment of the present invention, the differential CQI may be differentially encoded with respect to absolute CQIs (long-term wideband CQIs) of respective points in the measurement set (hereinafter referred to as "differential scheme two"). The two differential schemes can be expressed as follows:

the first difference scheme is as follows: ${\mathrm{\Δ}}_{i,j}={\mathrm{CQI}}_{i,j}-{\stackrel{\‾}{\mathrm{CQI}}}_{c_j,j}---\left(4\right)$

and a difference scheme II: ${\mathrm{\Δ}}_{i,j}={\mathrm{CQI}}_{i,j}-{\stackrel{\‾}{\mathrm{CQI}}}_{i,j}---\left(5\right)$

wherein, Delta_i，j、CQI_i，j、Short time differential CQI, short time CQI and long time wideband CQI of the channel from the ith point to the jth UE, respectively. For non-reference points, i.e. i ≠ c_jLong term wide band ofIs equal toCan be obtained by combining c in the formulas (1), (2) and (3)_jComputing CQI by substituting i_i，jAnd

note that the short-time CQI involved during the second period may be measured using any suitable technique now known or developed in the future. The scope of the invention is not limited in this respect.

In the differential scheme one, all short-time differential CQIs for each point in the measurement set are determined based on the same long-time wideband CQI (i.e., the absolute CQI for the reference point). Thus, according to this scheme, the short-time CQI for each point can be easily reconstructed at the base station. However, due to power imbalance issues in the CoMP measurement set, the short-time CQI of the neighboring point may differ greatly from the absolute CQI of the reference point, and therefore, the resulting differential result may have a large dynamic range. In one embodiment of the present invention, the feedback overhead can be further reduced by selecting the reference point as the point with the intermediate channel quality, thereby effectively reducing the dynamic range of the difference result.

In the second differential scheme, the short-term differential CQI for each point in the measurement set is determined based on the absolute CQI (long-term wideband CQI) for each point. Thus, the feedback overhead due to the aforementioned power imbalance problem can be controlled. However, since the long-term wideband CQI of each non-reference point is not directly fed back to the base station, the base station needs to estimate the long-term wideband CQI, which may bring some errors, resulting in some mismatches.

According to embodiments of the present invention, respective second channel state information may be transmitted to respective points in the measurement set. In this embodiment, the uplink feedback overhead may be spread out to various points in the measurement set. Each point may then aggregate the received channel state information to the designated point to reconstruct the CQI from the designated point.

According to another embodiment of the present invention, the second channel state information may still be transmitted to a designated point in the measurement set. In this way, the CQI for each point can be reconstructed from a given point (e.g., a point with a high computational power), and the reconstructed result can be transmitted to each point in the measurement set.

Those skilled in the art will appreciate that communication between the various points is easy to implement and is generally not limited by bandwidth, rate, etc.

The method 300 ends after step S302 is completed. By performing the method 300 at the UE, it can be seen that long-term and/or wideband channel state information and short-term and/or narrowband channel state information about various points in the measurement set are fed back to the base station in different time periods (stages). Specifically, in the first stage, only the first channel state information may be transmitted to a specified point in the measurement set, i.e., only one absolute CQI may be transmitted. Thus, the feedback overhead of the channel state information can be effectively reduced. In the second stage, the differential CQI aiming at each point in the measurement set is fed back, so that the feedback overhead can be further reduced, and simultaneously, the single-point CQI and the multi-point CQI are effectively supported, namely, the switching among SU-MIMO, MU-MIMO and CoMP can be supported.

It is important to note that although method 300 is shown in fig. 3 as ending after step S302, this is for illustrative and exemplary purposes only. In practice, the UE may perform steps S301 and S302 periodically. In other words, the method 300 or both steps S301 and S302 may be performed periodically.

In particular, the cycles performed in steps S301 and S302 may be different according to some embodiments of the present invention. For example, the feedback cycle of the first period for feeding back the first channel state information described above may be greater than or equal to the feedback cycle of the second period for feeding back the second channel state information. In other words, the first channel state information is transmitted less frequently than the second channel state information. Such an implementation is based on the consideration that long-term and/or wideband channel characteristics change less frequently than short-term and/or narrowband channel characteristics. By differently setting the feedback periods of the first stage and the second stage, the feedback overhead can be effectively reduced. Of course, the periodic relationship of the two periods is not limiting.

Reference is now made to fig. 4, which schematically illustrates a flow chart of a method 400 of acquiring channel state information at a base station in accordance with an exemplary embodiment of the present invention. The method 400 may be performed at a base station of a wireless communication system, e.g., by the base station itself or a component thereof, in accordance with embodiments of the present invention.

After the method 400 starts, first channel state information for a reference point in a measurement set is received at step S401. It should be understood that step S401 corresponds to step S301 in method 300. Thus, the description given above in connection with step S301 of method 300 with respect to the first channel state information applies equally to step S401. In particular, according to embodiments of the present invention, the first channel state information may relate to an absolute CQI between the UE and a reference point of the measurement set, which may indicate a long-term and/or wideband CQI of the channel, i.e. cell-specific channel characteristics.

The method 400 then proceeds to step S402, where the base station receives second channel state information for each point in the measurement set. It should be understood that step S402 corresponds to step S302 in method 300. Thus, the description given above in connection with step S302 of method 300 regarding the second channel state information applies equally to step S402. In particular, according to embodiments of the present invention, the second channel state information may relate to a differential CQI of the channel between the UE and the various points of the measurement set, which indicates short-time and/or narrowband channel characteristics, i.e. channel characteristics related to inter-cell cooperation.

It should be appreciated that as described above, the first and second channel state information need not be received by the base station directly from the UE, but the base station may also receive such information from other cooperating base stations in the measurement set.

The method 400 then proceeds to step S403. Here, the base station reconstructs channel state information for each point in the measurement set based on the received first and second channel state information. The base station performs different processing accordingly according to different differential coding schemes of the second channel state information.

If the second channel state information is encoded according to the first differential scheme, i.e., differentially encoded with respect to the absolute CQI of the reference point, the base station can easily reconstruct the CQI of each point. It can be calculated, for example, as:

the first difference scheme is as follows: ${\mathrm{CQI}}_{i,j}={\stackrel{\‾}{\mathrm{CQI}}}_{c_j,j}+{\mathrm{\Δ}}_{i,j}---\left(6\right)$

it can be seen that equation (6) corresponds to equation (4). Wherein,and Δ_i，jCan be obtained through two-stage feedback of the UE, therefore, for the first differential scheme, the base station does not need additional information to reconstruct CQI of each point.

If the second csi is encoded according to the second differential scheme, i.e. differentially encoded with respect to the absolute CQI of each point, the base station may reconstruct the csi according to the following equation:

and a difference scheme II: ${\mathrm{CQI}}_{i,j}={\stackrel{\‾}{\mathrm{CQI}}}_{i,j}+{\mathrm{\Δ}}_{i,j}---\left(7\right)$

it can be seen that equation (7) corresponds to equation (5). As mentioned earlier, due to the absolute CQI (Long term wideband CQI, i.e., the CQI) of each non-reference point) There is no direct feedback to the base station and therefore the base station needs to estimate it. The base station may estimate based on reciprocity of the uplink and downlink channels. For example, the long term wideband CQI for a non-reference point may be reconstructed as follows:

${\mathrm{CQI}}_{i,j}={\mathrm{\δ}}_{i,j}{\stackrel{\‾}{\mathrm{CQI}}}_{c_j,j},i\≠c_j---\left(8\right)$

wherein,_i，jis the ith and the c th points in the uplink_jThe compensation ratio of the received signal power at a point. To obtain_i，jThe considered signal power should be from the jth UE and is modified based on the reciprocity of FDD uplink and downlink.

Those skilled in the art will appreciate that the above-described manner of estimating the absolute CQI of the non-reference point is merely exemplary and may be estimated by those skilled in the art using any suitable technique now known or developed in the future. The scope of the invention is not limited in the above respects.

According to the embodiment of the present invention, the base station reconstructing the CQI of each point may be any one of the following: a serving base station, a primary transmission base station, a base station with the best channel quality, or a base station with stronger computing power.

From the above description of the method 300 and the method 400, those skilled in the art can understand that a new channel state information feedback mechanism is constructed between the base station and the UE according to the embodiment of the present invention. According to this mechanism, unlike the prior art, the channel state information feedback is done in two stages, each stage transmitting a different type of channel state information. Furthermore, only one absolute CQI, e.g. a long term and/or wideband CQI of the reference point, needs to be fed back to a specified point in the measurement set at the first stage. While the second stage may feed back differential CQIs for various points in the measurement set, e.g., indicating short-time and/or sub-band CQIs for various points. The feedback information transmitted in the two stages, respectively, is aggregated at the base station and used together to generate complete feedback information reflecting the overall channel conditions.

Reference is now made to fig. 5, which schematically illustrates a block diagram of an apparatus 500 for feeding back channel state information in a user equipment according to an exemplary embodiment of the present invention. In accordance with embodiments of the present invention, the apparatus 500 may reside at or otherwise be associated with one or more user equipments, UEs, of a wireless communication system. It is to be appreciated that the apparatus 500 is operable to perform the method 300 described above.

As shown in fig. 5, according to an embodiment of the present invention, the apparatus 500 includes a first feedback means 501 configured to feed back first channel state information for a reference point in a measurement set during a first period; and second feedback means 502 configured to feed back second channel state information for each point in the measurement set during a second time period.

According to an embodiment of the present invention, the first channel state information may include an absolute CQI of a channel between the UE and a reference point in the measurement set. The absolute CQI may be a wideband and/or a long-term CQI. Further, the second channel state information may include differential CQI for various points in the measurement set. The differential CQI may indicate a sub-band and/or a short-time CQI.

The second feedback means 502 may be configured to differentially encode the differential CQI in a variety of ways. According to an embodiment of the present invention, the differential CQI may be encoded using a differential scheme one, that is, differentially encoded with respect to an absolute CQI (long-term wideband CQI) of a reference point in the measurement set. According to another embodiment of the present invention, the differential CQI may be encoded using a differential scheme two, i.e. differentially encoded with respect to the absolute CQI (long-term wideband CQI) of the respective point in the measurement set.

The first feedback means 501 may be configured to feed back the first channel state information to a specified point in the measurement set, and the second feedback means 502 may be configured to feed back its respective second channel state information to each point in the measurement set, respectively. Optionally, the second feedback means 502 may be configured to feed back the second channel state information to a specified point in the measurement set.

The reference point in the measurement set may be any of: a service point, a primary transmission point, a point with the best channel quality, or a point with an intermediate channel quality. The specified point in the measurement set may be any of: a service point, a primary transmission point, a point with the best channel quality, or a point with high computational power. Both the reference point and the designated point may be selected by the serving point or recommended by the UE.

As mentioned above, the apparatus 500 as shown in fig. 5 may serve as an execution entity of the method 300 described above. Accordingly, various features described above in connection with fig. 3 are applicable to apparatus 500 and will not be described in detail herein.

Reference is now made to fig. 6, which schematically illustrates a block diagram of an apparatus 600 for acquiring channel state information at a base station, in accordance with an exemplary embodiment of the present invention. In accordance with embodiments of the present invention, the apparatus 600 may reside at or otherwise be associated with a base station of a wireless communication system. It is to be appreciated that the apparatus 600 is operable to perform the method 400 described above.

As shown in fig. 6, according to the embodiment of the present invention, the apparatus 600 includes a first receiving means 601 configured to receive first channel state information for a reference point in a measurement set; a second receiving means 602 configured to receive second channel state information for each point in the measurement set; and reconstructing means 603 configured to reconstruct the channel state information for each point in the measurement set based on the first channel state information and the second channel state information.

According to embodiments of the present invention, the first channel state information may relate to an absolute CQI between the UE and a reference point of the measurement set, which may indicate a long-term and/or wideband CQI of the channel, i.e. cell-specific channel characteristics. The second channel state information may relate to a differential CQI of the channel between the UE and the various points of the measurement set, which indicates short-time and/or narrow-band channel characteristics, i.e. channel characteristics related to inter-cell cooperation.

It should be appreciated that as described previously, the first and second channel state information need not be received by the base station directly from the UE, but the base station may also receive such information from other cooperating base stations in the measurement set.

The reconstruction means 603 performs different processing according to different differential encoding schemes of the second channel state information. For example, for the difference scheme one and the difference scheme two, the reconstructing device 603 may perform the reconstruction according to the step S403 described above, and details are not described here again.

The base station that reconstructs the channel state information may be any of: a serving base station, a primary transmission base station, a base station with the best channel quality, or a base station with high computing power. The base station then transmits the reconstructed results to each point in the measurement set.

As mentioned above, the apparatus 600 as shown in fig. 6 may serve as an execution entity of the method 400 described above. Accordingly, the various features described above in connection with fig. 4 are applicable to apparatus 600 and will not be described in further detail herein.

It should be understood that the division of the devices in the devices 500 and 600 is not limiting but exemplary. For example, the functions of a single device in the above description may be implemented by a plurality of devices. Conversely, multiple devices described above may be implemented by a single device. The scope of the invention is not limited in this respect.

It should also be understood that the various devices included in devices 500 and 600 may be implemented in a variety of ways including software, hardware, firmware, or any combination thereof. For example, in some embodiments, each of the apparatuses 500 and 600 may be implemented using software and/or firmware modules. Alternatively or additionally, each of the apparatuses 500 and 600 may also be implemented using hardware modules. For example, each of the apparatuses 500 and 600 may be implemented as an Integrated Circuit (IC) chip or an Application Specific Integrated Circuit (ASIC). Each of the apparatuses 500 and 600 may also be implemented as a system on a chip (SOC). Other ways, now known or later developed, are also feasible, and the scope of the present invention is not limited in this respect.

The foregoing has outlined rather broadly the principles and spirit of the invention in connection with a number of exemplary embodiments. Experiments prove that the feedback overhead of the wireless communication system can be effectively reduced by utilizing the method and the equipment according to the embodiment of the invention. Further, the accuracy of CQI feedback can be improved with limited feedback overhead. Further, the CQI feedback mechanism according to the embodiments of the present invention can support both single point transmission and CoMP transmission.

It should be noted that the flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and apparatus according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. It is to be understood that the drawings and the embodiments of the invention are designed solely for the purposes of illustration and not as a definition of the limits of the invention.

The methods disclosed in embodiments of the present invention may be implemented in software, hardware, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory for execution by a suitable instruction execution system, such as a microprocessor, Personal Computer (PC), or mainframe. In a preferred embodiment, the invention is implemented in software, which includes but is not limited to firmware, resident software, microcode, and the like.

It should be noted that the above description omits some more specific technical details that are well known to those skilled in the art and that may be necessary for the implementation of the embodiments of the present invention in order to make the embodiments of the present invention easier to understand. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will occur to those of ordinary skill in the art.

While several embodiments of the present invention have been described above, it should be understood by those skilled in the art that these descriptions are merely exemplary and illustrative. Many modifications and variations of the embodiments of the invention are possible in light of the above teachings and teachings without departing from the true spirit of the invention. Thus, the features described in the specification should not be considered as limiting. The scope of the invention is only limited by the appended claims.

Claims (28)

1. A method of feeding back channel state information in a user equipment, comprising:

during a first period, feeding back first channel state information for a reference point in a measurement set, wherein the reference point is any one of: a service point, a primary transmission point, a point with a best channel quality, or a point with an intermediate channel quality, and wherein the reference point is selected by the service point or recommended by the user equipment; and

feeding back second channel state information for each point in the measurement set during a second time period.

2. The method of claim 1, wherein:

the first channel state information comprises an absolute Channel Quality Indicator (CQI) of the reference point; and

the second channel state information comprises differential channel quality identities, CQIs, for respective points in the measurement set.

3. The method of claim 2, wherein the absolute CQI is a long-term wideband CQI determined by a weighting of a long-term wideband CQI of a previous subframe and a short-term wideband CQI of a current subframe.

4. The method of claim 3, wherein the short-time wideband CQI is calculated as:

${\mathrm{CQI}}_{c_j,j}=\frac{|u_j{H}_{c_j,j}{v}_{c_j,j}{|}^2}{{\mathrm{\σ}}_o^2}---\left(2\right),$ or

${\mathrm{CQI}}_{c_j,j}=\frac{|u_j{H}_{c_j,j}{v}_{c_j,j}{|}^2}{{\mathrm{\σ}}_{f,j}^2}---\left(3\right)$

Wherein,is from the c th_jThe short-time broadband CQI points to the jth UE and is in the current subframe;is from the c th_jA channel from a point to a jth UE; u. of_jIs the predicted receive beamformer at the jth UE;is from the jth UE to the c_jFeedback PMI of a point;is noise plus interference outside the CoMP measurement set; andis the noise plus the overall interference of the jth UE.

5. The method of claim 2, wherein the differential CQI is differentially encoded relative to an absolute CQI for the reference point calculated as:

${\mathrm{\Δ}}_{i,j}={\mathrm{CQI}}_{i,j}-{\stackrel{\‾}{CQI}}_{c_j,j}---\left(4\right)$

wherein, Delta_i，j、CQI_i，jRespectively is the short-time differential CQI and the short-time CQI of the channel from the ith point to the jth UE;is from the c th_jLong-term wideband CQI for the channel that points to the jth UE.

6. The method of claim 2, wherein the differential CQI is differentially encoded with respect to an absolute CQI for the respective point, calculated as:

${\mathrm{\Δ}}_{i,j}={\mathrm{CQI}}_{i,j}-{\stackrel{\‾}{CQI}}_{i,j}---\left(5\right)$

wherein, Delta_i,j、CQI_i,j、Short time differential CQI, short time CQI and long time wideband CQI of the channel from the ith point to the jth UE, respectively.

7. The method of claim 1, wherein the first channel state information is fed back to designated points in the measurement set, and their respective second channel state information is fed back to respective points in the measurement set.

8. The method of claim 1, wherein the first channel state information is fed back to a designated point in the measurement set and the second channel state information is fed back to the designated point.

9. The method of claim 7 or 8, wherein the specified point is any of: a service point, a main transmission point, a point with the best channel quality, or a point with strong computing power; and the specified point is selected by a service point or recommended by the user device.

10. A method of acquiring channel state information at a base station, comprising:

receiving first channel state information for a reference point in a measurement set, wherein the reference point is any one of: a service point, a primary transmission point, a point with a best channel quality, or a point with an intermediate channel quality, and wherein the reference point is selected by the service point or recommended by the user equipment;

receiving second channel state information for each point in the measurement set; and

reconstructing channel state information for each point in the measurement set based on the first and second channel state information.

11. The method of claim 10, wherein:

the first channel state information comprises an absolute Channel Quality Indicator (CQI) of the reference point; and

the second channel state information comprises differential channel quality identities, CQIs, for respective points in the measurement set.

12. The method of claim 11, wherein the differential CQI is differentially encoded relative to an absolute CQI for the reference point, the reconstructing channel state information for each point in the measurement set calculated as:

${\mathrm{CQI}}_{i,j}={\stackrel{\‾}{CQI}}_{c_j,j}+{\mathrm{\Δ}}_{i,j}---\left(6\right)$

wherein, Delta_i，j、CQI_i，jRespectively is the short-time differential CQI and the short-time CQI of the channel from the ith point to the jth UE;is from the c th_jLong-term wideband CQI for the channel that points to the jth UE.

13. The method of claim 11, wherein the differential CQI is differentially encoded with respect to absolute CQI for respective points, the reconstructing channel state information for respective points in the measurement set calculated as:

${\mathrm{CQI}}_{i,j}={\stackrel{\‾}{CQI}}_{i,j}+{\mathrm{\Δ}}_{i,j}---\left(7\right)$

wherein, Delta_i,j、CQI_i,j、Short time differential CQI, short time CQI and long time wideband CQI of the channel from the ith point to the jth UE, respectively.

14. The method according to any of claims 10-13, wherein the base station is any of: a serving base station, a primary transmission base station, a base station with the best channel quality, or a base station with high computing power.

15. An apparatus for feeding back channel state information in a user equipment, comprising:

first feedback means configured to feedback, during a first period, first channel state information for a reference point in a measurement set, wherein the reference point is any one of: a service point, a primary transmission point, a point with a best channel quality, or a point with an intermediate channel quality, and wherein the reference point is selected by the service point or recommended by the user equipment; and

second feedback means configured to feed back second channel state information for each point in the measurement set during a second time period.

16. The apparatus of claim 15, wherein:

the first channel state information comprises an absolute Channel Quality Indicator (CQI) of the reference point; and

the second channel state information comprises differential channel quality identities, CQIs, for respective points in the measurement set.

17. The apparatus of claim 16, wherein the absolute CQI is a long-term wideband CQI determined by a weighting of a long-term wideband CQI of a previous subframe and a short-term wideband CQI of a current subframe.

18. The apparatus of claim 17, wherein the short-time wideband CQI is calculated as:

${\mathrm{CQI}}_{c_j,j}=\frac{|u_j{H}_{c_j,j}{v}_{c_j,j}{|}^2}{{\mathrm{\σ}}_o^2}---\left(2\right),$ or

${\mathrm{CQI}}_{c_j,j}=\frac{|u_j{H}_{c_j,j}{v}_{c_j,j}{|}^2}{{\mathrm{\σ}}_{f,j}^2}---\left(3\right)$

Wherein,is from the c th_jThe short-time broadband CQI points to the jth UE and is in the current subframe;is from the c th_jA channel from a point to a jth UE; u. of_jIs the predicted receive beamformer at the jth UE;is from the jth UE to the c_jFeedback PMI of a point;is noise plus interference outside the CoMP measurement set; andis the noise plus the overall interference of the jth UE.

19. The apparatus of claim 16, wherein the differential CQI is differentially encoded relative to an absolute CQI for the reference point calculated as:

${\mathrm{\Δ}}_{i,j}={\mathrm{CQI}}_{i,j}-{\stackrel{\‾}{CQI}}_{c_j,j}---\left(4\right)$

wherein, Delta_i,j、CQI_i,jRespectively is the short-time differential CQI and the short-time CQI of the channel from the ith point to the jth UE;is from the c th_jLong-term wideband CQI for the channel that points to the jth UE.

20. The apparatus of claim 16, wherein the differential CQI is differentially encoded with respect to an absolute CQI for a respective point, calculated as:

${\mathrm{\Δ}}_{i,j}={\mathrm{CQI}}_{i,j}-{\stackrel{\‾}{CQI}}_{i,j}---\left(5\right)$

wherein, Delta_i,j、CQI_i,j、Short of the channel from the ith point to the jth UE, respectivelyA time differential CQI, a short-time CQI, and a long-time wideband CQI.

21. The apparatus according to claim 15, wherein the first feedback means is configured to feed back the first channel state information to a specified point in the measurement set, and the second feedback means is configured to feed back its respective second channel state information to respective points in the measurement set, respectively.

22. The apparatus according to claim 15, wherein the first feedback means is configured to feed back the first channel state information to a specified point in the measurement set, and the second feedback means is configured to feed back the second channel state information to the specified point.

23. The apparatus of claim 21 or 22, wherein the specified point is any of: a service point, a main transmission point, a point with the best channel quality, or a point with strong computing power; and the specified point is selected by a service point or recommended by the user device.

24. An apparatus for acquiring channel state information at a base station, comprising:

first receiving means configured to receive first channel state information for a reference point in a measurement set, wherein the reference point is any one of: a service point, a primary transmission point, a point with a best channel quality, or a point with an intermediate channel quality, and wherein the reference point is selected by the service point or recommended by the user equipment;

second receiving means configured to receive second channel state information for each point in the measurement set; and

a reconstruction device configured to reconstruct channel state information for each point in the measurement set based on the first and second channel state information.

25. The apparatus of claim 24, wherein:

the first channel state information comprises an absolute Channel Quality Indicator (CQI) of the reference point; and

the second channel state information comprises differential channel quality identities, CQIs, for respective points in the measurement set.

26. The apparatus of claim 25, wherein the differential CQI is differentially encoded relative to an absolute CQI for the reference point, the reconstructing means configured to reconstruct channel state information for each point in the measurement set as:

${\mathrm{CQI}}_{i,j}={\stackrel{\‾}{CQI}}_{c_j,j}+{\mathrm{\Δ}}_{i,j}---\left(6\right)$

wherein, Delta_i,j、CQI_i,jRespectively is the short-time differential CQI and the short-time CQI of the channel from the ith point to the jth UE;is from the c th_jLong-term wideband CQI for the channel that points to the jth UE.

27. The apparatus according to claim 25, wherein the differential CQI is differentially encoded with respect to absolute CQI for respective points, the reconstructing means being configured to reconstruct channel state information for respective points in the measurement set according to:

${\mathrm{CQI}}_{i,j}={\stackrel{\‾}{CQI}}_{i,j}+{\mathrm{\Δ}}_{i,j}---\left(7\right)$

wherein, Delta_i,j、CQI_i,j、Short time differential CQI, short time CQI and long time wideband CQI of the channel from the ith point to the jth UE, respectively.

28. The apparatus according to any of claims 24-27, wherein the base station is any of: a serving base station, a primary transmission base station, a base station with the best channel quality, or a base station with high computing power.