Channel state information feedback method and deviceTechnical Field
The present invention relates to an Advanced Long Term Evolution (LTE-a) system technology, and in particular, to a method and an apparatus for feeding back channel state information.
Background
In wireless communication, if multiple antennas are used at a transmitting end (e.g., node eNB), a spatial multiplexing method may be used to increase a transmission rate, that is, different antennas on the same time-frequency resource at the transmitting end transmit different data. Multiple antennas are also used at the receiving end (e.g., user terminal UE), and in one case, in the case of a single user, resources of all antennas are allocated to the same user, that is, a user equipment independently occupies physical resources allocated to the user equipment within a transmission interval, and this transmission form is called single-user MIMO (SU-MIMO); another case is that resources of different antenna spaces are allocated to different users in the case of multiple users, that is, a user equipment and at least one other user equipment share physical resources allocated to the user equipments in a transmission interval, and a user equipment and other user equipments share the same physical resource through space division multiple access or space division multiplexing, where the physical resource may be a time-frequency resource, and this transmission form is called multi-user MIMO (MU-MIMO).
In Long Term Evolution (LTE) of the third generation partnership project standards organization (3GPP), a UE is set to transmit based on one of the following transmission modes (transmission modes) through a semi-static (semi-static) signaling by a higher layer:
mode 1: single antenna port: port 0(Single-antenna port: port 0);
mode 2: transmit diversity (Transmit diversity);
mode 3: open-loop spatial multiplexing (Open-loop spatial multiplexing);
mode 4: closed-loop spatial multiplexing (Closed-loop spatial multiplexing);
mode 5: multi-user multiple input multiple output (Multi-user MIMO);
mode 6: closed-loop Rank (Rank) 1precoding (Closed-loop Rank 1 precoding);
mode 7: single antenna port: port 5(Single-antenna port: Port 5).
The user terminal (UE) feeds back different channel state information to the sending end according to different transmission modes, then the sending end (eNB) carries out scheduling according to the channel state information fed back by the UE, and new channel state information is configured for actual transmission according to a certain principle (such as a maximum capacity principle). Wherein the fed back channel state information comprises: channel Quality Indication (CQI) information, Precoding Matrix Indicator (PMI) information, and Rank Indicator (RI) information. Wherein,
the CQI is an index for measuring the quality of a downlink channel. In the 36-213 protocol, the CQIs are expressed by integer values of 0 to 15, and represent different CQI levels, and the different CQIs correspond to respective modulation schemes and coding rates (MCSs).
And the RI is used for describing the number of the space independent channels and the rank of the corresponding channel response matrix. In the open-loop spatial multiplexing mode and the closed-loop spatial multiplexing mode, the UE needs to feed back RI information, and in other modes, the RI information does not need to be fed back.
The PMI refers to an index number of a precoding codebook fed back by the UE. In 3 modes of closed-loop spatial multiplexing, MU-MIMO, and closed-loop with RI being 1, PMI information needs to be fed back, and PMI information is not fed back in other transmission modes.
The fed back channel state information includes: CQI information, PMI information, and RI information.
In the LTE system, the feedback of CQI/PMI, RI may be periodic feedback or aperiodic feedback, and the specific feedback is shown in table 1:
| scheduling modes | Periodic CQI reporting channel | Aperiodic CQI reporting channel |
| Frequency non-selectivity | PUCCH | |
| Frequency selectivity | PUCCH | PUSCH |
TABLE 1
In table 1, for the CQI/PMI and RI fed back periodically, if the UE does not need to transmit data, the CQI/PMI and RI fed back periodically are transmitted in a format2/2a/2b (PUCCH format2/2a/2b) on a Physical Uplink Control Channel (PUCCH), and if the UE needs to transmit data, the CQI/PMI and RI are transmitted in a Physical Uplink Shared Channel (PUSCH); for the CQI/PMI and RI with aperiodic feedback, the transmission is only carried out on the PUSCH.
When PMI reporting is performed, the UE reports one or more PMIs. The UE is limited to carry out PMI and RI reporting in a precoding codebook specified by a bit mapping parameter codebook Subset rule (codebook Subset Restriction) configured by a high layer.
According to the semi-static configuration of the high layer, the UE feeds back the CQI/PMI/RI information periodically on the PUCCH physical channel, and the feedback mode adopted is shown in table 2.
TABLE 2
CQI/PMI and RI reporting types with four different periodicity and offset in each PUCCH reporting mode:
reporting type 1 CQI feedback supporting terminal selection of subbands
Report type 2 support for wideband CQI and PMI feedback
Report type 3 support of RI feedback
Report type 4 support wideband CQI
High Layer configured (sub-band CQI) feedback and Multiple PMI feedback are not supported on the PUCCH channel.
In a multi-antenna system, the bit overhead of directly feeding back the channel response matrix is too large, or the channel response matrix is decomposed, such as SVD, so as to obtain the optimal precoding matrix for feeding back, and the overhead is still large. Therefore, some precoding codebook sets known to the transceiving end need to be constructed, the obtained optimal precoding matrix is compared with the coding matrix in the precoding codebook set, and the index value corresponding to the most approximate precoding codebook is selected for feedback, so that bit overhead can be greatly saved. The index values of these fed-back precoding codebooks are the PMIs.
The above important channel information: the feedback types of PMI/RI/CQI in uplink are divided into the following two types:
and periodic feedback, which is mainly carried on the uplink control channel PUCCH.
Aperiodic feedback, which is feedback carried on the uplink shared channel PUSCH.
The periodic feedback is necessarily configured, the aperiodic feedback is aperiodic trigger type feedback, and the aperiodic feedback on the PUSCH is high-precision feedback, belongs to auxiliary feedback and is used for improving the precision.
The Long Term Evolution Advanced (LTE-a) system, as an Evolution standard of LTE, supports a larger system bandwidth (up to 100MHz), and is backward compatible with the existing standard of LTE. In order to obtain higher average spectral efficiency of a cell and improve coverage and throughput of a cell edge, based on an existing LTE system, LTE-a supports downlink to at most 8 antennas, and some feedback enhancement techniques are proposed in terms of codebook feedback, mainly to enhance the feedback accuracy of a codebook and compress overhead by utilizing time correlation and/or frequency domain correlation of channel information. The technology can improve the spectrum utilization rate of an evolution International Mobile Telecommunications-advanced (IMT-Advance) system and relieve the shortage of spectrum resources.
In the LTE-a system, the channel state information feedback roughly includes: firstly, a base station sends pilot frequency to UE, and the pilot frequency is used for the UE to estimate a downlink channel; then, UE estimates the downlink channel according to the pilot signal, and determines the channel state information including RI, PMI and CQI; and finally, the UE feeds back the channel state information to the base station according to the feedback mode.
In summary, in LTE-a, in the transmission mode supporting SU/MU, among the wideband/multi-subband channel information that needs to be fed back, the channel information that may need to be transmitted includes RI, PMI and CQI, where the PMI information may include two precoding indicators, i1 and i 2.
In summary, in LTE-a, in the transmission mode supporting SU/MU, among the wideband/multi-subband channel information that needs to be fed back, the channel information that may need to be transmitted includes RI, PMI and CQI, where the PMI information may include i1 and i 2. Since two precoding indicators i1 and i2 need to be fed back in LTE-a, a channel state information feedback method in which only one PMI value is transmitted in a PUCCH channel in an LTE system, specifically a method for calculating CQI information and PMI information, cannot be applied to new technical requirements in LTE-a. However, in the prior art, no implementation scheme of how to feed back CQI information and PMI information in channel state information in an LTE-a system is provided.
Disclosure of Invention
In view of the above, the present invention provides a method and an apparatus for feeding back channel state information, which can ensure that the channel state information is fed back normally in an LTE-a system, thereby ensuring that a communication system works normally.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a channel state information feedback method comprises the following steps:
user Equipment (UE) determines channel state information; wherein, the channel state information comprises one or any combination of the following information: rank Indicator (RI) information, Channel Quality Indicator (CQI) information and Precoding Matrix Indicator (PMI) information;
and periodically feeding back the determined channel state information to the base station through a Physical Uplink Control Channel (PUCCH).
The CQI information and the PMI information are respectively obtained by RI information calculation;
the PMI information includes: first precoding matrix indicator i1 information and/or second precoding matrix indicator i2 information.
The periodically feeding back the determined channel state information to the base station through the PUCCH comprises the following steps:
when the channel state information comprises RI information, CQI information and PMI information, the RI information and first precoding matrix indicator information i1 are jointly coded and exist in the same report type; the CQI information and second precoding matrix indicator information i2, present in another report type;
alternatively, the RI information is encoded independently, and exists in one report type; the CQI information, first precoding matrix indicator information i1, and second precoding matrix indicator information i2, are present in another report type;
alternatively, the CQI information may be present independently in one report type.
The channel state information determined by the feedback specifically includes:
the UE jointly calculates CQI information and i2 information according to the RI value fed back finally and the i1 information fed back finally, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE calculates and obtains CQI information, i1 information and i2 information according to the RI value fed back finally, and feeds back the obtained CQI information, i1 information and i2 information to the base station; or,
the UE jointly calculates CQI information and i2 information according to the lowest RI value and the fixed i1 value in the bit mapping parameter codebook subset rule, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE jointly calculates CQI information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule and the last fed back i1 information, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE calculates and obtains CQI information, i1 information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule, and feeds back the obtained CQI information, i1 information and i2 information to the base station; or,
the UE jointly calculates CQI information and i2 information according to the RI value and the fixed i1 value which are fed back finally, and feeds back the obtained CQI information and i2 information to the base station; or,
and the UE calculates and obtains CQI information according to the RI value of 1 and feeds the obtained CQI information back to the base station.
Wherein the bit mapping parameter codebook subset rule is obtained by high-level configuration;
a channel state information feedback apparatus, comprising at least: a processing module and a feedback module, wherein,
a processing module, configured to determine channel state information, where the channel state information includes one or any combination of the following information: RI information, CQI information, PMI information;
and the feedback module is used for periodically feeding back the determined channel state information to the base station through the PUCCH.
The processing module is further configured to receive a pilot from the base station, and estimate a downlink channel according to the pilot signal.
The PMI information includes first precoding matrix indicator i1 information and second precoding matrix indicator i2 information; the processing module is specifically configured to:
performing joint coding on the RI information and the i1 information, and calculating according to the RI and i1 joint information to obtain CQI information or i2 information; or,
independently coding the RI information, and calculating to obtain i1 information, CQI information and i2 information according to the RI coding information; or,
and calculating to obtain CQI information according to the RI value of 1.
The processing module is specifically configured to:
according to the RI value fed back finally and the i1 information fed back finally, the CQI information and the i2 information are obtained through common calculation, and the obtained CQI information and the i2 information are output to a feedback module; or,
calculating to obtain CQI information, i1 information and i2 information according to the RI value fed back finally, and outputting the obtained CQI information, i1 information and i2 information to a feedback module; or,
according to the lowest RI value and the fixed i1 value in the bit mapping parameter codebook subset rule, the CQI information and the i2 information are obtained through common calculation, and the obtained CQI information and the i2 information are output to a feedback module; or,
according to the lowest RI value in the bit mapping parameter codebook subset rule and the last fed back i1 information, the CQI information and the i2 information are obtained through common calculation, and the obtained CQI information and the i2 information are output to a feedback module; or,
calculating to obtain CQI information, i1 information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule, and outputting the obtained CQI information, i1 information and i2 information to a feedback module; wherein the bit mapping parameter codebook subset rule is obtained by high-level configuration; or,
according to the RI value fed back finally and the fixed i1 value, the CQI information and the i2 information are obtained through common calculation, and the obtained CQI information and the i2 information are output to a feedback module; or,
and calculating to obtain CQI information according to the RI value of 1, and outputting the obtained CQI information to a feedback module.
It can be seen from the above technical solutions provided by the present invention that the method includes that the UE determines channel state information; and periodically returning the determined channel state information to the base station through the PUCCH. Wherein, the channel state information comprises one or any combination of the following information: RI information, CQI information, PMI information. Where PMI information may include i1 and i 2. The invention provides a technical scheme for feeding back the channel state information in the LTE-A system and ensures the normality of the channel state information feedback. Further, even when the RI information or the RI and i1 joint coding information is lost, the normal feedback of the channel state information is ensured by the method of the invention, thereby ensuring the normal work of the communication system.
Drawings
Fig. 1 is a feedback diagram of a CSI feedback mode 1 during downlink periodic feedback in LTE-a;
fig. 2 is a feedback diagram of a CSI feedback mode 2 during downlink periodic feedback in LTE-a;
FIG. 3 is a flow chart of a channel state information feedback method according to the present invention;
fig. 4 is a schematic diagram of a structure of a csi feedback apparatus according to the present invention.
Detailed Description
In the LTE-a system, considering that the main application of 8 antennas will be the dual polarization case, the codebook design and enhancement need to fully consider the characteristics of the dual polarization channel. The main idea of the feedback technology of the enhanced codebook is that the overhead of PMI feedback is increased compared with LTE feedback, and the feedback of two PMIs is used to jointly represent the state information of a channel, and the method mainly includes two implementation modes: double codebooks and double PMI feedback are defined, or equivalent single codebook and double PMI feedback of the double codebooks are defined.
Defining dual codebooks and dual PMI feedback includes: the structure of precoding/feedback for one subband consists of two matrices. Each of the two matrices is subordinate to a separate codebook. The codebook is known in advance by both the base station and the UE. The code words fed back may vary at different times and on different subbands. One matrix represents the properties of the wideband or long-term channel. Another matrix representation determines the properties of the channel over the frequency band or the short time. The matrix codebook used is represented in the form of a finite set of countable matrices and each matrix is known to both the UE and the base station. One of the matrices may be a fixed matrix, requiring no feedback. This is equivalent to degrading to a single codebook feedback (possibly used in the case of high rank and low rank uncorrelated channels).
The feedback of the channel information is based on a double codebook structure as follows: for one subband or multiple joint subbands needing to feed back channel information, the UE feeds back two pieces of PMI information (in some cases, it is not necessary to feed back at the same time, and one PMI may also be predefined as a fixed value without feedback) to the base station, which are first precoding matrix indicator information (i1) and second precoding matrix indicator information (i2), respectively, where i1 corresponds to a codeword W1 in one codebook C1, and i2 corresponds to a codeword W2 in another codebook C2. The base station side has the same information of C1 and C2, finds corresponding code words W1 and W2 from corresponding codebooks C1 and C2 after receiving i1 and i2, and calculates W-F (W1, W2) according to an agreed function rule F to obtain channel information W.
The above dual codebook design criterion is a specific codebook form in LTE-a. In concrete implementation, only codebooks corresponding to W1 and W2 need to be defined, but a virtual codebook corresponding to W exists in reality, and many performance considerations in design are considered based on the codebook corresponding to W. Further, the design of codebook feedback has two important parts, the first important part is the specific structure, overhead and specific codeword of W, which directly relates to the performance of double codebook feedback (although the feedback forms defined specifically are feedback W1 and W2, and do not directly feed back W), and the consideration of this part is similar for both single codebook and double codebook forms. The second important part is how to divide W into 2 codebooks to show the characteristic of being more adaptive to the channel time domain/frequency domain variation, thereby effectively saving the cost. This is a cost saving consideration for double codebooks, which single codebooks do not have.
In addition to the above dual codebook implementation, there is a single codebook feedback approach equivalent to using dual codebooks, dual PMI feedback, etc.: a dual codebook equivalent single codebook and dual PMI feedback are defined.
For Rank r, r is an integer, which is different from the previous 4Tx codebook in that when using the dual codebook equivalent single codebook feedback, the feedback of 2 PMIs are required to indicate the information of the code word in the corresponding codebook, and the dual codebook equivalent single codebook can be generally expressed as shown in table 3 below:
TABLE 3
In Table 3Is a group i1i2The code words, which are commonly indicated, can be written in the functional form W (i)1,i2)，
Only i needs to be determined1i2And (4) finishing. For example, when r is 1, vm＝[1 ej2πm/32 ej4πm/32 ej6πm/32]TEquivalent to table 4 below.
TABLE 4
In fact, the way of defining the dual codebook equivalent single codebook and dual PMI feedback is equivalent to the dual codebook dual PMI, the only difference is that in this method, two codebooks C1 and C2 are not defined, but instead, a codebook corresponding to W composed of dual codebooks and their functional relationships is defined, that is, the virtual codebook is actually defined instead of C1 and C2.
In LTE-a, in the transmission mode supporting SU/MU, among wideband/multi-subband channel information that needs to be fed back, channel information that may need to be transmitted includes RI, PMI and CQI, where the PMI information may include two precoding indicators, i1 and i 2.
The PMI and CQI information fed back periodically can be calculated by the RI information fed back finally, and when the RI information is completely lost, the minimum RI value given by the bit mapping parameter codebook subset rule codebook is adopted for calculation. Specifically, when the RI information of the first feedback period is lost, there will be no last RI information fed back that can be referred to, and then the PMI and CQI information of the first feedback period are calculated by taking the smallest possible RI value. Wherein the bit mapping parametric codebook subset rule (codebook subset rule) is obtained by a high level configuration.
When channel state information is fed back in an LTE-a system, the CSI feedback mode 1 and the CSI feedback mode 2 are included. In CSI feedback mode 1, RI information and i1 information are jointly encoded and transmitted in the same subframe at a relatively long period. And the CQI information and the i2 information are transmitted in a relatively short period in the other sub-frame. As shown in particular in figure 1. In the CSI feedback mode 2, RI information is independently encoded and transmitted in a relatively long period within one subframe; the CQI information is transmitted with i1 and i2 at another subframe with a relatively short period. As shown in particular in fig. 2.
Fig. 3 is a flowchart of a channel state information feedback method according to the present invention, as shown in fig. 3, including:
step 300: the UE determines channel state information. Wherein, the channel state information comprises one or any combination of the following information: RI information, CQI information, PMI information.
And the CQI information and the PMI information are respectively obtained by RI information calculation.
In this step, the PMI information includes: i1 information and/or i2 information. The CQI information or the i2 information is obtained by the joint information calculation of RI and i1 respectively;
alternatively, the i1 information is obtained by RI information calculation; the i2 information is obtained by RI information calculation; the CQI information is obtained by RI information calculation;
or, the CQI information is obtained by calculating RI as 1;
the RI information and the i1 information may be jointly encoded, or the RI information may be independently encoded.
Step 301: and periodically feeding back the determined channel state information to the base station through the PUCCH.
In the LTE-a system, the feedback of the channel state information may include a CSI feedback mode 1 and a CSI feedback mode 2. When the CSI feedback mode 1 is used, that is, when the channel state information includes RI information, CQI information, and PMI information, the RI information and i1 information are jointly encoded and transmitted in a relatively long period in the same subframe; while the CQI information and the i2 information are transmitted in a relatively short period in another subframe, that is, the RI information and the i1 information jointly encoded in the same report type, and the i2 information and the CQI information exist in the same report type, specifically as shown in fig. 1, fig. 1 is a feedback diagram of a CSI feedback mode 1 during downlink period feedback in LTE-a;
in the CSI feedback mode 2, RI information is independently encoded and transmitted in a relatively long period within one subframe; the CQI information, i1, and i2 are transmitted in another subframe at a relatively short period, that is, the RI information exists in one report type, and the i1 information, i2 information, and CQI information exist in the same report type, specifically as shown in fig. 2, fig. 2 is a feedback diagram of CSI feedback mode 2 during downlink periodic feedback in LTE-a.
In this step, feeding back the determined channel state information specifically includes:
the UE jointly calculates CQI information and i2 information according to the RI value fed back finally and the i1 information fed back finally, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE calculates and obtains CQI information, i1 information and i2 information according to the RI value fed back finally, and feeds back the obtained CQI information, i1 information and i2 information to the base station; or,
the UE jointly calculates CQI information and i2 information according to the lowest RI value and the fixed i1 value in the bit mapping parameter codebook subset rule, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE jointly calculates CQI information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule and the last fed back i1 information, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE calculates and obtains CQI information, i1 information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule, and feeds back the obtained CQI information, i1 information and i2 information to the base station; or,
the UE jointly calculates the CQI information and the i2 information according to the RI value and the fixed i1 value which are finally fed back, and feeds back the obtained CQI information and the i2 information to the base station; or,
and the UE calculates and obtains the CQI information according to the RI value of 1 and feeds the obtained CQI information back to the base station.
By determining the RI information or the i1 information used for calculating the CQI information and the i2 information, the normal feedback of the CQI and/or the i2 information is ensured when the RI information or the RI and i1 joint information is lost, thereby ensuring the normal operation of the whole communication system.
The specific implementation means of this step is easily available to those skilled in the art, and is not used to limit the protection scope of the present invention, and will not be described herein again.
The method of the invention also comprises the following steps: and the base station sends pilot frequency to the UE, and the pilot frequency is used for the UE to estimate a downlink channel. The specific implementation is within the skill of those in the art and will not be described further herein.
The apparatus for feeding back the csi according to the method of the present invention, as shown in fig. 4, at least comprises a processing module and a feedback module, wherein,
a processing module, configured to determine channel state information, where the channel state information includes one or any combination of the following information: RI information, CQI information, PMI information. The method is specifically used for: the PMI information comprises i1 information and/or i2 information; performing joint coding on the RI information and the i1 information, and calculating according to the RI information and the i1 joint information to obtain CQI information or i2 information; or, independently coding the RI information, and calculating according to the RI information to obtain CQI information, i1 information and i2 information; or, the CQI information is obtained by calculation according to the RI value of 1.
And the feedback module is used for periodically returning the determined channel state information to the base station through the PUCCH.
The processing module is specifically configured to:
according to the RI value fed back finally and the i1 information fed back finally, the CQI information and the i2 information are obtained through common calculation, and the obtained CQI information and the i2 information are output to a feedback module; or,
calculating to obtain CQI information, i1 information and i2 information according to the RI value fed back finally, and outputting the obtained CQI information, i1 information and i2 information to a feedback module; or,
according to the lowest RI value and the fixed i1 value in the bit mapping parameter codebook subset rule, the CQI information and the i2 information are obtained through common calculation, and the obtained CQI information and the i2 information are output to a feedback module; or,
according to the lowest RI value in the bit mapping parameter codebook subset rule and the last fed back i1 information, the CQI information and the i2 information are obtained through common calculation, and the obtained CQI information and the i2 information are output to a feedback module; or,
calculating to obtain CQI information, i1 information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule, and outputting the obtained CQI information, i1 information and i2 information to a feedback module; wherein the bit mapping parameter codebook subset rule is obtained by high-level configuration; or,
according to the RI value fed back finally and the fixed i1 value, the CQI information and the i2 information are obtained through common calculation, and the obtained CQI information and the i2 information are output to a feedback module; or,
and calculating to obtain CQI information according to the RI value of 1, and outputting the obtained CQI information to a feedback module.
The channel state information device can be arranged in the UE.
The process of the present invention will be described in detail with reference to examples.
In a first embodiment, assuming that channel state information is fed back periodically on a PUCCH in an LTE-a communication system, as shown in fig. 1, when a feedback mode 1-1 is adopted and RI and i1 are jointly coded, a UE feeds back channel state information including RI information, i1 information, i2 information and CQI information.
In the first embodiment, RI information and i1 information are jointly encoded and transmitted in the same subframe at a relatively long period; the CQI information and the i2 information are transmitted in additional sub-frames with a relatively short period. The CQI information and the i2 information in the channel state information are calculated according to the RI and i1 joint information fed back last. When the fed back RI/i1 information is lost, in particular, when all previously fed back RI and i1 joint information is lost, the UE calculates and feeds back the channel state information according to one of the following methods:
the UE jointly calculates CQI information and i2 information according to the lowest RI value and the fixed i1 value in the bit mapping parameter codebook subset rule, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE calculates and obtains CQI information, i1 information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule, and feeds back the obtained CQI information, i1 information and i2 information to the base station; or,
and the UE calculates and obtains the CQI information according to the RI value of 1 and feeds the obtained CQI information back to the base station.
Second embodiment, assuming that channel state information is fed back periodically on PUCCH in LTE-a system, as shown in fig. 2, when feedback mode 1-1 is adopted and CSI feedback mode 2 is switched to CSI feedback mode 1, the UE feeds back channel state information including RI information, i1 information, i2 information and CQI information.
In the second embodiment, the CSI feedback mode 1 refers to that RI information and i1 information are jointly encoded and transmitted in a relatively long period within the same subframe; the CQI information and the i2 information are transmitted in additional sub-frames with a relatively short period. The CSI feedback mode 2 refers to that RI information is independently encoded and transmitted in a relatively long period within one subframe; the CQI information is transmitted with i1 and i2 at another subframe with a relatively short period.
In the CSI feedback mode 2, the CQI information, the i1 information, and the i2 information in the channel state information are calculated according to the last RI information fed back; in the CSI feedback mode 1, the CQI information and the i2 information in the channel state information are calculated according to the RI and i1 joint information fed back last, respectively. Specifically, when the fed-back RI/i1 joint information is lost after the transition to the CSI feedback mode 1, and particularly, when all the previously fed-back RI and i1 joint information are lost, the UE calculates and feeds back the channel state information according to one of the following methods:
the UE jointly calculates CQI information and i2 information according to the RI value fed back finally and the i1 information fed back finally, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE calculates and obtains CQI information, i1 information and i2 information according to the RI value fed back finally, and feeds back the obtained CQI information, i1 information and i2 information to the base station; or,
the UE jointly calculates CQI information and i2 information according to the lowest RI value and the fixed i1 value in the bit mapping parameter codebook subset rule, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE jointly calculates CQI information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule and the last fed back i1 information, and feeds back the obtained CQI information and i2 information to the base station; or,
the UE calculates and obtains CQI information, i1 information and i2 information according to the lowest RI value in the bit mapping parameter codebook subset rule, and feeds back the obtained CQI information, i1 information and i2 information to the base station; or,
the UE jointly calculates the CQI information and the i2 information according to the RI value and the fixed i1 value which are finally fed back, and feeds back the obtained CQI information and the i2 information to the base station; or,
and the UE calculates and obtains the CQI information according to the RI value of 1 and feeds the obtained CQI information back to the base station.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, and any modifications, equivalents, improvements, etc. that are within the spirit and principle of the present invention should be included in the present invention.