CN102546113B - LTE channel measurement and feedback method - Google Patents
LTE channel measurement and feedback method Download PDFInfo
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Abstract
The invention discloses an LTE (Long Term Evolution) channel measurement and feedback method suitable for the CoMP (Coordinated Multi-Point) working mode. A base station configures CSI-RS resources for signal transmission points in the CoMP; a terminal performs channel measurement on the signal transmission points according to the CSI-RS resources, and feed the signal transmission points of which the signal-to-noise ratio satisfies the preset condition back to the base station; the base station selects the signal transmission points according to the feedback information of the terminal and the given working information of the base station side, and sets one or more measurement assumptions and corresponding CSI-RS resources; the terminal performs further channel measurement and feeds back the measurement information according to the measurement assumptions and the corresponding CSI-RS resources; and if the measurement information fed back by the terminal can not determine the resource dispatching mode, the terminal repeatedly performs measurement and feedback till the base station can determine the resource dispatching mode for resource dispatching. The method provided by the invention solves the problem in the prior art that the terminal has large calculated amount due to coexistence of various measurement assumptions.
Description
Technical Field
The invention relates to the field, in particular to a channel measurement and feedback method of LTE.
Background
The Long Term Evolution (LTE) project is an Evolution of 3G that improves and enhances the over-the-air access technology of 3G. OFDM (Orthogonal frequency division Multiplexing) and MIMO (Multiple-input Multiple-output) are adopted as the only standards for wireless network evolution. The peak rates of 100Mbit/s at the downlink and 50Mbit/s at the uplink can be provided under the 20MHz spectrum bandwidth. The performance of cell edge users is improved, the cell capacity is increased, and the system delay is reduced.
In Rel 11, coordinated multi-point (CoMP) is a MIMO technique, and a signal that is originally an interference is converted into a signal that can contribute to performance improvement by cooperation of a plurality of signal transmission points. CoMP is a branch of MIMO technology and is common to other types of usage, but has unique considerations due to differences in the manner of operation.
The power distribution problem is as follows: in conventional MIMO systems, since the individual antennas are placed at the base station, their transmit power is limited by the total base station power. For CoMP, the power limit at each eNB/RRH may be different, thus leading to different optimization conclusions. For example, a constant power designed codebook is appropriate.
CoMP implementation methods are divided into two main categories: jointly process the JP mode and the coordinated Scheduling/Beamforming (CS/CB) mode. The JP method is characterized in that each transmission point of the terminal data in the CoMP coordination set may transmit the terminal data. The CS/CB scheme is characterized in that terminal data only exists in a serving cell, but the decision of scheduling/beamforming is made uniformly under coordination of all cells of a CoMP transmission point set where the terminal performs channel measurement.
The measurement of the channel information by the terminal is mainly based on CSI-RS resources, in LTE Rel 10, the possible positions of CSI-RS with different antenna port numbers in an LTE frame structure are added with the period information which possibly appears at the positions to form a CSI-RS resource configuration, the base station informs each terminal of which configuration is to be selected for the terminal to measure the channel by using a high-level signaling, if the terminal has fast channel change during real-time measurement, the corresponding configuration period is needed to be shorter, the channel change is fast, or the long-term channel statistical characteristic is averaged, the configured period can be set longer to save the resources.
Method for terminal to have following measurement information and feedback
Explicit channel feedback: the content of the explicit feedback includes a channel part and a noise and interference part, wherein the channel part feeds back the channel state seen by the receiving end, one or more channel characteristics of each cell in the measurement set need to be reported in one subframe, including an instantaneous channel matrix, a statistical transmission channel correlation matrix and a main eigenvalue part of the instantaneous channel, the feedback of the noise and interference part may be interference outside the cell reported by the terminal or outside a CoMP transmission cell, or total received power, or a correlation matrix of the noise and interference, etc
Implicit channel feedback: implicit feedback defines different feedback modes for different assumptions, such as single-user or multi-user MIMO, single-cell or cooperative transmission, single point (CB/CS) transmission or multipoint (JP) transmission, etc. The feedback of the report single cell PMI or the multi-cell PMI by JP, the CB/CS can feed back the PMIs of the report single cell or a plurality of single cells, and can also feed back other types of information except the PMI, such as characteristic values and the like.
SRS feedback by using uplink and downlink channel symmetry in a TDD system: the terminal sends the SRS through the symmetry of the channel, which can be used as the eNB to estimate the channel state information, and this method is particularly suitable for the TDD system.
The implicit channel feedback is a feedback method mainly adopted, but different signal information is caused by adopting different assumptions, and the feedback is complicated because multiple CoMP methods are supported.
Fig. 1 is a schematic diagram of a CoMP operating mode including 2 cells; as shown in fig. 1, after the base station configures the relevant resources and the measurement hypothesis, the feedback information after the terminal performs the channel measurement is shown in table one.
Watch 1
As can be seen from the table i, due to the coexistence of multiple hypotheses, the terminal computation amount is large, and at the same time, the uplink feedback amount increases, which results in an excessive system load. Moreover, for this operation mode of CoMP, in order to ensure that a certain interfering transmission point can be found, it is necessary to arrange as many transmission points as possible for the terminals to perform measurement, so that as the number of participating base stations increases, the number of associated terminals increases, and the complexity thereof increases nonlinearly.
In summary, in the CoMP operation mode in the prior art, when channel measurement and feedback are performed, multiple measurement hypotheses coexist, which results in a large calculation amount for the terminal.
Disclosure of Invention
The invention provides a channel measurement and feedback method of LTE (Long term evolution), which solves the problems of coexistence of multiple measurement hypotheses and large terminal calculation amount in the prior art.
The invention discloses a channel measurement and feedback method of LTE, which is suitable for a CoMP working mode and comprises the following steps:
step 1: a base station configures channel state information measurement pilot frequency CSI-RS resources for each signal transmission point in a CoMP, and transmits configuration information of the CSI-RS resources to a terminal;
step 2: the terminal performs channel measurement operation on each signal transmitting point in CoMP according to the configuration information of the CSI-RS resource, and performs sequencing according to the acquired signal-to-noise ratio; feeding back the signal transmitting points with the signal-to-noise ratios meeting the preset conditions to the base station;
and step 3: the base station selects a signal transmitting point according to the feedback information of the terminal and the known working information of the base station side, and sets one or more measuring hypotheses and corresponding CSI-RS resources for the terminal according to the selected signal transmitting point; sending the measurement hypothesis and configuration information of the corresponding CSI-RS resource to a terminal;
and 4, step 4: the terminal carries out further channel measurement according to the measurement hypothesis and the corresponding CSI-RS resource, and feeds back the measurement information of the selected signal transmitting point to the base station; the base station performs resource pre-scheduling according to the feedback information of the terminal, if the measurement information fed back by the terminal can not determine the resource scheduling mode, the base station repeats step 3, and if the measurement information fed back by the terminal can determine the resource scheduling mode, step 5 is executed;
and 5: and the base station carries out resource scheduling according to the determined resource scheduling mode.
In the above method, feeding back the signal transmitting point whose signal-to-noise ratio satisfies the preset condition to the base station includes:
sorting the received signal transmitting points from large to small according to the signal-to-noise ratio, and selecting all the signal transmitting points within a certain attenuation range by taking the maximum signal-to-noise ratio as a reference;
or
Sorting the received signal transmitting points according to the signal-to-noise ratio from large to small, and selecting all the signal transmitting points exceeding a certain power range by taking the interference of the signal transmitting points outside the corresponding CoMP area as a reference;
or,
sequencing the received signal transmitting points from large to small according to the signal-to-noise ratio, taking the maximum signal-to-noise ratio as a reference, and taking other signal transmitting points as interference sources; dividing interference sources into signal sources one by one according to the signal-to-noise ratio from strong to weak until the combined signal-to-noise ratio reaches a specified value; wherein, all signal emission points in the signal source are selected signal emission points;
or,
sequencing the received signal transmitting points from large to small according to the signal-to-noise ratio, taking the maximum signal-to-noise ratio as a reference, and taking other signal transmitting points as interference sources; dividing interference sources into signal sources one by one according to the signal-to-noise ratio from strong to weak until the variable quantity of two adjacent signal-to-noise ratio combining operations is smaller than a specified value; wherein, all signal emission points in the signal source are selected signal emission points;
and feeding back the measurement information of the selected signal transmitting point to the base station.
In the above method, feeding back the signal transmitting point whose signal-to-noise ratio satisfies the preset condition to the base station includes:
the base station configures a specific signal transmitting point as a reference point through high-level signaling, sorts the signal-to-noise ratios of the received signal transmitting points from large to small, and takes all signal transmitting points with the signal-to-noise ratios larger than the signal-to-noise ratio of the reference point as selected signal transmitting points.
In the above method, the feeding back measurement information of the selected signal transmission point to the base station includes:
and the terminal feeds back the ID of the signal transmitting point meeting the preset condition and the number of the signal transmitting points to the base station.
In the above method, the feeding back, by the terminal, the ID of the signal transmission point satisfying the preset condition to the base station includes:
the terminal feeds back the ID of the CSI-RS resource contained in the CSI-RS resource configuration information corresponding to the selected signal transmitting point to the base station,
and the base station corresponds to the ID of the signal transmitting point through the ID of the CSI-RS resource.
In the above method, the selecting, by the base station, the signal transmission point according to the feedback information of the terminal and the known working information of the base station side includes:
and the base station selects the signal transmitting points with uncertain resource scheduling modes from the signal transmitting points fed back by the terminal according to the information of the signal transmitting points fed back by the terminal and the known working information of the base station side.
In the above method, the measurement assumption includes:
the information of the selected signal transmitting points, the information of the signal transmitting points with the determined states and the preferential CoMP working mode.
In the above method, the setting one or more measurement hypotheses for the terminal according to the selected signal transmission point includes:
when a plurality of signal transmission points are selected by the base station,
when the selected signal transmission point belongs to three sectors of a cell, the relative time offset or frequency offset is less than a specified value, and the priority CoMP working mode set by the base station for the terminal is as follows: performing channel measurement according to a JT mode;
when the selected signal emission point belongs to different station addresses and the relative time offset or frequency offset is greater than a specified value, the preferential CoMP working mode set by the base station for the terminal is as follows: and performing channel measurement according to a CS/CB mode.
In the above method, the setting one or more measurement hypotheses for the terminal according to the selected signal transmission point includes:
when the plurality of transmitting points fed back by the plurality of terminals are all the macro base station as the strongest transmitting point, the priority CoMP working mode set by the base station for the terminals is as follows: and closing the signal transmitting point of the macro base station by taking the cell splitting gain as a priority principle.
In the above method, the setting one or more measurement hypotheses for the terminal according to the selected signal transmission point includes:
when the base station has determined the resource scheduling mode of part of the signal transmission points, the base station sets the measurement hypothesis by using the information of the determined signal transmission points as the interference parameters affecting the rest of the terminals.
In summary, the invention firstly arranges the CSI-RS for each signal transmitting point through the base station to perform long-term characteristic channel measurement, and firstly screens out part of the signal transmitting points which have influence on the terminal. By determining which transmitting points may have influence and feeding back the influence to the base station, the base station is helped to effectively eliminate improper working assumptions according to actual conditions. The requirement on the configuration period can be reduced, more transmission points can be accommodated, and the implementation of the CoMP scheme is facilitated. The base station gradually determines the working assumption and then carries out real channel measurement corresponding to data transmission, so that the calculation workload of the terminal can be effectively reduced, the invalid calculation quantity is reduced by eliminating the working assumption with low possibility, and the burden of uplink wireless transmission is also reduced.
Drawings
Fig. 1 is a schematic diagram of a CoMP operating mode including 2 cells;
FIG. 2 is a flow chart of a channel measurement and feedback method of LTE in the present invention;
FIG. 3 is a detailed flowchart of a channel measurement and feedback method of LTE in the present invention;
fig. 4 is a schematic diagram illustrating the operation of multiple cells in a CoMP mode according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Fig. 2 is a flowchart of a channel measurement and feedback method of LTE in the present invention, as shown in fig. 2,
step 201: step 1: a base station configures channel state information measurement pilot frequency CSI-RS resources for each signal transmission point in a CoMP, and transmits configuration information of the CSI-RS resources to a terminal;
step 202: the terminal performs channel measurement operation on each signal transmitting point in CoMP according to the configuration information of the CSI-RS resource, and performs sequencing according to the acquired signal-to-noise ratio; feeding back the signal transmitting points with the signal-to-noise ratios meeting the preset conditions to the base station;
step 203: the base station selects a signal transmitting point according to the feedback information of the terminal and the known working information of the base station side, and sets one or more measuring hypotheses and corresponding CSI-RS resources for the terminal according to the selected signal transmitting point; sending the measurement hypothesis and configuration information of the corresponding CSI-RS resource to a terminal;
step 204: the terminal carries out further channel measurement according to the measurement hypothesis and the corresponding CSI-RS resource, and feeds back the measurement information of the selected signal transmitting point to the base station; the base station performs resource pre-scheduling according to the feedback information of the terminal, if the measurement information fed back by the terminal cannot determine the resource scheduling mode, the base station repeats step 203, and if the measurement information fed back by the terminal can determine the resource scheduling mode, step 205 is performed;
step 205: and the base station carries out resource scheduling according to the determined resource scheduling mode.
FIG. 3 is a detailed flowchart of a channel measurement and feedback method of LTE in the present invention; as shown in figure 3 of the drawings,
step 301, a base station configures a CSI-RS resource for a channel measurement long-term characteristic for each signal transmission point in a CoMP coordination area, and sends configuration information of the CSI-RS resource to each terminal.
In step 301, the base station side configures a CSI-RS resource for measuring the channel long-term characteristics for each signal transmission point in a CoMP coordination area, and the base station side stores a correspondence between the signal transmission point and the CSI-RS resource. Namely, the base station side can locally acquire the ID of the signal transmitting point corresponding to the CSI-RS resource through the ID of the CSI-RS resource in the CSI-RS resource configuration information fed back by the terminal.
Step 302, the terminal carries out channel measurement on all signal transmitting points according to CSI-RS resources without any measurement hypothesis; and screening out signal transmitting points influencing the terminal, and feeding back the signal transmitting points to the base station.
In step 302, the terminal performs channel measurement operation on each signal transmission point according to the CSI-RS resource configured by the base station, collects the signal-to-noise ratio of each signal transmission point, sorts the signal transmission points according to the obtained signal-to-noise ratios from large to small, and screens out the signal transmission points affecting the terminal through a certain rule.
The signal transmitting point having influence means that a signal transmitted by the signal transmitting point has influence on the terminal, and the signal transmitting point may be a macro base station or a micro base station serving the terminal, that is, a signal source; and may also be a signal transmission point, i.e. an interference source, which causes interference to the data transmission of the terminal.
In an embodiment of the present invention, the received signal transmitting points are sorted from large to small according to the signal-to-noise ratio, and all signal transmitting points within a certain attenuation range are selected based on the maximum signal-to-noise ratio. Wherein, the certain attenuation range can be set according to the configuration of the base station or the actual network deployment condition; the attenuation range may be 3db, for example.
Or sequencing the received signal transmitting points from large to small according to the signal-to-noise ratio, and selecting all the signal transmitting points exceeding a certain power range by taking the interference of the signal transmitting points outside the corresponding CoMP area as a reference; the signal transmitting point measurement set comprises all signal transmitting points to be considered, the signal transmitting points outside the corresponding CoMP area correspond to interference generated by signals of transmitting points outside the RRM measurement set, and the terminal does not have independent reference symbol resources to measure all the signal transmitting points outside the CoMP area, so that only the whole effect can be measured. For example, wherein the power range beyond a certain is 3dB
In another embodiment of the invention, the received signal transmitting points are sorted from large to small according to the signal-to-noise ratio, the maximum signal-to-noise ratio is taken as a reference, and other signal transmitting points except the maximum signal-to-noise ratio are taken as interference sources; dividing interference sources into signal sources one by one according to the signal-to-noise ratio from strong to weak, and combining the signal-to-noise ratios until the combined signal-to-noise ratio reaches a specified value, for example, 3 dB. Wherein the combined signal-to-noise ratio is calculated by the formulaCalculating; wherein, PMergingFor combined signal-to-noise ratio, PSignal sourceSum of detected received powers, P, of all valid signals of a plurality of signal sources for combiningInterference sourceFor measuring the sum of the detected received powers, P, of a plurality of interferers outside the set of transmission pointsNoise(s)Is the noise power.
In other embodiments of the present invention, the received signal transmitting points are sorted from large to small according to the signal-to-noise ratio, and the signal transmitting points except the maximum signal-to-noise ratio are used as interference sources based on the maximum signal-to-noise ratio; dividing interference sources into signal sources one by one according to the signal-to-noise ratio from strong to weak, and carrying out combined signal-to-noise ratio operation until the variation of the combined signal-to-noise ratio operation of two adjacent times is smaller than a specified value, such as 1 dB.
And all the signal transmitting points which are drawn into the signal source are selected signal transmitting points.
In other screening embodiments of the present invention, the received signal transmitting points are sorted from large to small according to the signal-to-noise ratio, the signal transmitting point corresponding to the received maximum signal-to-noise ratio is used as a signal source, the other signal transmitting points are used as interference sources, and the interference sources are eliminated one by one, wherein, assuming that the base station closes transmission without interference power, the combined signal-to-noise ratio is calculated, and when the obtained combined signal-to-noise ratio is greater than a set value, or the variation of two adjacent calculations is smaller than a specified value; and taking all signal sources in the combined signal-to-noise ratio and the power-off emission point as selected signal emission points. Wherein, the obtained combined signal-to-noise ratio is greater than a set value, which may specifically be: if the SNR level meets a certain bit error rate for a specific transmission mode, for example, with a 64QAM modulation scheme, without coding, and the bit error rate is 0.1, it is assumed that the corresponding-2 dB is transmitted under the gaussian channel.
In a preferred embodiment of the present invention, the base station configures a specific signal transmission point as a reference point through a high-level signaling, sorts the signal-to-noise ratios of the received signal transmission points from large to small, and selects all signal transmission points having a signal-to-noise ratio greater than that of the reference point as selected signal transmission points.
The terminal selects the signal transmitting points which affect the terminal according to a specific screening mode, wherein the selected signal transmitting points can be a signal source or an interference source. And feeding back the signal transmitting points to the base station, specifically, feeding back the ID of the selected signal transmitting points and the number of the signal transmitting points to the base station by the terminal. In the specific embodiment of the invention, the terminal can simultaneously feed back the ID of the signal transmitting points and the number of the signal transmitting points, or can successively feed back the ID of the signal transmitting points and the number of the signal transmitting points; for example, the number of signal transmission points is fed back first, and then the base station arranges resources to feed back the ID of the corresponding signal transmission point. According to different feedback modes, the method is divided into feedback of high-layer signaling and feedback of physical layer scheduling information.
And 303, the base station selects a proper measurement hypothesis for the terminal according to the working information stored at the base station side and the measurement information preliminarily fed back by the terminal.
In step 303, the base station sets one or more measurement hypotheses for the terminal according to the known working information of the base station side, and by combining the ID of the signal transmission point fed back by the terminal and the number of the signal transmission points meeting the preset condition. The working information comprises scheduling information which is stored by a base station side and used for resource scheduling and scheduling parameters which are configured in advance by the base station side; the measurement assumptions include: the information of the selected signal transmitting points, the information of the signal transmitting points with the determined states and the preferential CoMP working mode.
Under the condition that the resource scheduling mode of part of signal transmission points is determined, the influence of the part of signal transmission points on the terminal can be determined; e.g. it is already occupied to serve another terminal and cannot accommodate a new terminal, then it is certainly interference for the measuring terminal and the interference vector has been determined and can be transmitted to the terminal as interference parameter. The scheduling parameters pre-configured by the base station side comprise information such as position information, coverage, transmission coverage under a specific vector, logical connection of a macro cell/a micro cell and the like of a signal transmission point stored by the base station side.
In the CoMP operating mode, each measurement hypothesis is applicable to different operating scenarios, and in an embodiment of the present invention, different measurement hypotheses are set by determining different signal transmission points where association may occur:
when the number of signal transmitting points fed back by the terminal is 1, the base station sets the terminal to perform channel measurement according to a single-cell mode;
when a plurality of signal transmitting points are selected by the base station, the base station can select the signal transmitting points according to specific situations,
when the selected signal transmission point belongs to three sectors of a cell and the relative time offset or frequency offset is smaller than a specified value, the base station sets a preferential CoMP working mode for the terminal in the measurement hypothesis set by the base station as follows: performing channel measurement according to a JT mode; in an embodiment of the present invention, the JT pattern may be designated when the relative frequency offset is less than 5%.
When the selected signal emission point belongs to different station addresses and the relative time offset or frequency offset is greater than a specified value, the preferential CoMP working mode set by the base station for the terminal is as follows: and performing channel measurement according to a CS/CB mode. In an embodiment of the present invention, the relative frequency offset is greater than 5%, and a CS/CB mode may be specified.
In other embodiments of the present invention, when the number of signal transmission points fed back by the base station is greater than 4, the base station sets for the terminal, and performs channel measurement in a macro diversity manner. Because the feedback information amount may be so large that CoMP cannot work when the number of terminal feedbacks is greater than 4, the measurement assumption of macro diversity transmission may be directly adopted, or the terminal is not scheduled on the relevant PRB resources, and the terminal is temporarily abandoned from being configured with a new measurement assumption.
When the plurality of transmitting points fed back by the plurality of terminals are all the macro base station as the strongest signal transmitting point, the priority CoMP working mode set by the base station for the terminal is as follows: and closing the signal transmitting point of the macro base station by taking the cell splitting gain as a priority principle. When a plurality of terminals include a signal transmission point of a macro base station and the signal transmission point of the macro base station is used as a main interference source, if the terminals are distributed in different directions, it can be preferentially assumed that the transmission power of the macro base station is turned off to obtain cell split capacity gain, and if the terminals are distributed in approximately the same direction, it can be preferentially assumed that a beam forming direction is shifted away from the direction, so that when the terminals are prevented from being interfered, services for other terminals are provided at the same time.
The base station may set one or more measurement hypotheses for the terminal according to actual situations, and is not limited in the above embodiments.
And step 304, the base station configures the CSI-RS resource for the selected signal transmission point to measure the real-time characteristics of the channel, and sends the configured measurement hypothesis and the configuration information of the corresponding CSI-RS resource to the terminal.
In step 304, the base station selects a signal transmission point with an uncertain resource scheduling mode from the signal transmission points fed back by the terminal according to the information of the signal transmission points fed back by the terminal and the known work information of the base station side. All or part of channel parameters of the signal transmitting points of the uncertain resource scheduling mode can not be determined until further measurement is needed to obtain additional measurement information. And the base station takes the information of the signal transmitting points capable of determining the resource scheduling mode as interference parameters influencing other terminals. The interference parameters are set in the measurement hypothesis and signaled to the terminal.
After setting one or more measurement hypotheses for each terminal, the base station sends the one or more measurement hypotheses and configuration information of corresponding CSI-RS resources to the terminal. The measurement hypothesis and the configuration information of the CSI-RS resource sent to the terminal comprise: the CoMP measurement method includes the following steps of CoMP working mode information, measurement information of a signal transmission point known by a base station side, state information of the signal transmission point on a corresponding PRB, transmission precoding vector information of the signal transmission point, variation parameters of a transmission vector of the signal transmission point, adjustment parameters of transmission power, and other parameters which can be used for measuring a channel in detail, such as detailed channel information of a part of terminals, variation information of the signal transmission point, and the like.
And 305, the terminal remeasures the channel state on the corresponding CSI-RS resource according to the newly configured measurement hypothesis, and feeds back the obtained measurement information to the base station.
In step 305, the terminal performs further signal measurement operation on the selected signal transmission point on the configured CSI-RS resource according to one or more measurement hypotheses configured by the base station to obtain channel state information of the signal transmission point with the best capacity. In an embodiment of the present invention, the terminal acquires parameters such as a Rank Indicator (RI), a Precoding Matrix Indicator (PMI), a Channel Quality Indicator (CQI), and the like during the re-channel measurement operation, and feeds back the parameters to the base station.
The base station performs resource pre-scheduling according to the feedback information of the terminal, if the measurement information fed back by the terminal can not determine the resource scheduling mode, the base station repeats steps 303 to 305, and if the measurement information fed back by the terminal can determine the resource scheduling mode, step 306 is executed; repeating the steps 303-305, and gradually reducing the range of the measurement hypothesis through repeated measurement for multiple times until the measurement information fed back by the terminal can determine the resource scheduling mode; that is, until a signal transmitting point providing service for a terminal is selected, the measurement information of the signal transmitting point is fed back to a base station.
In other embodiments of the present invention, the assumed range may be gradually narrowed by first determining measurement parameters of some terminals, and using these determined measurement parameters as interference parameters affecting other terminals, and transmitting the interference parameters from the base station to the relevant terminals.
And step 306, the base station makes a final scheduling decision according to the carefully measured channel information and arranges the transmission of the Physical Downlink Shared Channel (PDSCH).
In step 306, the base station obtains a signal transmitting point for providing service to the terminal according to the detailed measurement information fed back by the terminal, and configures resources for performing PDSCH transmission on the signal transmitting point.
Fig. 4 is a schematic diagram illustrating the operation of multiple cells in a CoMP mode according to the present invention, as shown in fig. 4,
the figure has 5 transmitting points, namely a macro cell A, a macro cell B and three micro cells m, n and k in the macro cell A; the macro cells are all configured with 4 antenna ports, the micro cells are all configured with 2 antenna ports, and the terminal is provided with double antennas. The base station adopts the configuration arrangement of R10CSI-RS resources, a macro cell A adopts 4 antenna port position configuration 1, a macro cell B adopts 4 antenna port configuration 2, three micro cells m, a micro cell n and a micro cell k respectively adopt 2 antenna port position configuration 0, 5 and 10, and the period is 50 ms.
The first step is as follows: and the base station side configures CSI-RS resources for each signal transmitting point in the CoMP area, performs channel measurement, and issues configuration information of the CSI-RS resources to the terminals 1 to 7.
The second step is that: the method comprises the steps that the terminals 1-7 carry out channel measurement operation on each signal transmitting point according to CSI-RS resource configuration information sent by a base station, the signal-to-noise ratio of each signal transmission is obtained, sorting is carried out according to the obtained signal-to-noise ratios, and the signal transmitting points meeting preset conditions are selected and fed back to the base station; wherein, the terminal detects the SNR of all the corresponding 5 transmitting points, the conditions are as follows,
the terminal 1 feeds back 4 antenna configuration ports 1 and 2 antenna port configuration 0 belonging to a set of signal transmitting points which can affect the terminal, and the base station side searches a corresponding relation according to the ID of the CSI-RS resource in the configured CSI-RS resource configuration information to obtain a macro cell A and a micro cell m;
similarly, it is obtained that the terminal 2 is significantly affected by the macro cell a and the micro cell n, the terminal 3 is affected by the macro cell a, the macro cell B and the micro cell k, the terminal 4 is affected by the macro cell a only, and the terminal 5 is affected by the macro cell B only; both terminals 6, 7 are affected by macro cell a and macro cell B. And each terminal feeds back the measurement information obtained by the primary measurement to the base station.
The third step: and the base station selects a signal transmitting point according to the feedback information of the terminal and the known working information of the base station side, and sends the measurement hypothesis and the configuration information of the corresponding CSI-RS resource to the terminal.
The physical position information of the micro cell m, the micro cell n and the micro cell k can be recorded at the base station side in advance, and the base station knows that the approximate coverage areas of the micro cell m, the micro cell n and the micro cell k are in the same direction of the base station, so that the interference to the area can be avoided by adopting the mode of turning off the transmission or the beam forming; the micro cell k is not good in frequency characteristic due to the cost problem, and is not suitable for JT operation with the macro cell B because the distance time difference with the macro cell is large, and the current situation is that the user density of the cell A is large, and a mode capable of obtaining cell capacity splitting gain is preferentially selected.
And the base station sets one or more measurement hypotheses for the terminal according to the selected signal transmitting points. Wherein,
the terminal 4 and the terminal 5 only feed back one signal transmission point, and the configured measurement is assumed to be single cell measurement on the fed back signal transmission point.
Both the terminal 6 and the terminal 7 feed back the macro cell a and the macro cell B, and the configured measurement assumes that single-cell measurement of two cells is performed respectively to find their respective optimal precoding vectors.
After the optimal precoding vectors of the terminal 6 and the terminal 7 are determined, the information of the signal transmission points of the macro base stations corresponding to the terminal 6 and the terminal 7 is used as the interference parameters affecting the signals of the micro cells m, n, and k, and in the newly configured measurement hypothesis, the transmission of the optimal precoding vectors of the terminal 4 and the terminal 5 to the terminal 1, the terminal 2, and the terminal 3 corresponds to the null direction. And decides not to schedule terminal 6, terminal 7 and terminal 1, terminal 2, terminal 3 at the same time.
And sending the optimal pre-coding vectors of the terminal 4 and the terminal 5 to other terminals as a part of measurement assumptions, wherein the measurement assumptions respectively configured for the terminal 1, the terminal 2 and the terminal 3 are that single-cell measurement is respectively carried out in a micro cell m, a micro cell n and a micro cell k, and the respective optimal pre-coding vectors of the terminals are searched and corresponding channel quality information is obtained.
In addition, for the terminal 6, the terminal 7 is configured with other measurement hypotheses to perform multi-user JT pairing parameter measurement, and performs capacity comparison with the measurement hypotheses that respectively adopt the optimal transmission vector, and selects a JT or CB mode to operate according to a capacity optimization principle.
Until the best channel transmission mode of each signal transmitting point is determined, the best resource allocation mode is determined.
In summary, the invention firstly arranges the CSI-RS for each signal transmitting point through the base station to perform long-term characteristic channel measurement, and firstly screens out part of the signal transmitting points which have influence on the terminal. By determining which transmitting points may have influence and feeding back the influence to the base station, the base station is helped to effectively eliminate improper working assumptions according to actual conditions. The requirement on the configuration period can be reduced, more transmission points can be accommodated, and the implementation of the CoMP scheme is facilitated. The base station gradually determines the working assumption and then carries out real channel measurement corresponding to data transmission, so that the calculation workload of the terminal can be effectively reduced, the invalid calculation quantity is reduced by eliminating the working assumption with low possibility, and the burden of uplink wireless transmission is also reduced.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.
Claims (8)
1. A channel measurement and feedback method for LTE is characterized in that the method is suitable for a multi-point coordinated CoMP working mode, and the method comprises the following steps:
step 1: a base station configures channel state information measurement pilot frequency CSI-RS resources for each signal transmission point in a CoMP, and transmits configuration information of the CSI-RS resources to a terminal;
step 2: the terminal performs channel measurement operation on each signal transmitting point in CoMP according to the configuration information of the CSI-RS resource, and performs sequencing according to the acquired signal-to-noise ratio; feeding back the signal transmitting points with the signal-to-noise ratios meeting the preset conditions to the base station;
and step 3: the base station selects a signal transmitting point according to the feedback information of the terminal and the known working information of the base station side, and sets one or more measuring hypotheses and corresponding CSI-RS resources for the terminal according to the selected signal transmitting point; sending the measurement hypothesis and configuration information of the corresponding CSI-RS resource to a terminal;
and 4, step 4: the terminal carries out further channel measurement according to the measurement hypothesis and the corresponding CSI-RS resource, and feeds back the measurement information of the selected signal transmitting point to the base station; the base station performs resource pre-scheduling according to the feedback information of the terminal, if the measurement information fed back by the terminal can not determine the resource scheduling mode, the base station repeats the step 3 and the step 4, and if the measurement information fed back by the terminal can determine the resource scheduling mode, the step 5 is executed;
and 5: the base station carries out resource scheduling according to the determined resource scheduling mode;
wherein, the feeding back the signal transmitting point of which the signal-to-noise ratio meets the preset condition to the base station comprises:
sorting the received signal transmitting points from large to small according to the signal-to-noise ratio, and selecting all the signal transmitting points within a certain attenuation range by taking the maximum signal-to-noise ratio as a reference; feeding back the selected signal transmitting point to the base station;
or,
sorting the received signal transmitting points according to the signal-to-noise ratio from large to small, and selecting all the signal transmitting points exceeding a certain power range by taking the interference of the signal transmitting points outside the corresponding CoMP area as a reference; feeding back the selected signal transmitting point to the base station;
or,
sequencing the received signal transmitting points from large to small according to the signal-to-noise ratio, taking the maximum signal-to-noise ratio as a reference, and taking other signal transmitting points except the signal transmitting point corresponding to the maximum signal-to-noise ratio as interference sources; dividing interference sources into signal sources one by one according to the signal-to-noise ratio from strong to weak until the combined signal-to-noise ratio reaches a specified value; wherein, all the signal transmitting points which are divided into the signal source are selected signal transmitting points; feeding back the selected signal transmitting point to the base station;
or,
sequencing the received signal transmitting points from large to small according to the signal-to-noise ratio, taking the maximum signal-to-noise ratio as a reference, and taking other signal transmitting points except the signal transmitting point corresponding to the maximum signal-to-noise ratio as interference sources; dividing interference sources into signal sources one by one according to the signal-to-noise ratio from strong to weak until the variable quantity of two adjacent signal-to-noise ratio combining operations is smaller than a specified value; wherein, all the signal transmitting points which are divided into the signal source are selected signal transmitting points; feeding back the selected signal transmitting point to the base station;
or,
the base station configures a specific signal transmitting point as a reference point through high-level signaling, sorts the signal-to-noise ratios of the received signal transmitting points from large to small, and takes all signal transmitting points with the signal-to-noise ratios larger than the signal-to-noise ratio of the reference point as selected signal transmitting points.
2. The method of claim 1, wherein feeding back the selected signal transmission point to the base station comprises:
and the terminal feeds back the ID of the signal transmitting point meeting the preset condition and the number of the signal transmitting points to the base station.
3. The method of claim 2, wherein the terminal feeding back the ID of the signal transmission point satisfying the preset condition to the base station comprises:
the terminal feeds back the ID of the CSI-RS resource contained in the CSI-RS resource configuration information corresponding to the selected signal transmitting point to the base station,
and the base station acquires the ID of the corresponding signal transmitting point through the ID of the CSI-RS resource.
4. The method of claim 1, wherein the base station selecting the signal transmission point according to the feedback information of the terminal and the known operation information of the base station comprises:
and the base station selects the signal transmitting points with uncertain resource scheduling modes from the signal transmitting points fed back by the terminal according to the information of the signal transmitting points fed back by the terminal and the known working information of the base station side.
5. The method of claim 1, wherein the measurement hypothesis comprises:
the information of the selected signal transmitting points, the information of the signal transmitting points with the determined states and the preferential CoMP working mode.
6. The method of claim 5, wherein setting one or more measurement hypotheses for the terminal according to the selected signal transmission point comprises:
when the base station selects a plurality of signal transmission points,
when the selected signal transmission point belongs to three sectors of a cell, the relative time offset or frequency offset is less than a specified value, and the priority CoMP working mode set by the base station for the terminal is as follows: performing channel measurement according to a joint processing JT mode;
when the selected signal emission point belongs to different station addresses and the relative time offset or frequency offset is greater than a specified value, the preferential CoMP working mode set by the base station for the terminal is as follows: and carrying out channel measurement according to a coordinated scheduling/beamforming CS/CB mode.
7. The method of claim 6, wherein setting one or more measurement hypotheses for the terminal according to the selected signal transmission point comprises:
when the plurality of transmitting points fed back by the plurality of terminals are all the macro base station as the strongest signal transmitting point, the priority CoMP working mode set by the base station for the terminal is as follows: and closing the signal transmitting point of the macro base station by taking the cell splitting gain as a priority principle.
8. The method of claim 7, wherein setting one or more measurement hypotheses for the terminal according to the selected signal transmission point comprises:
when the base station has determined the resource scheduling mode of part of the signal transmission points, the base station sets the measurement hypothesis by using the information of the determined signal transmission points as the interference parameters affecting the other terminals.
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