CN103369694A

CN103369694A - A self-adaptive physical downlink control channel (PDCCH) format selecting method

Info

Publication number: CN103369694A
Application number: CN2012100908436A
Authority: CN
Inventors: 金明; 吕伯轩
Original assignee: Potevio Institute of Technology Co Ltd
Current assignee: Potevio Institute of Technology Co Ltd
Priority date: 2012-03-30
Filing date: 2012-03-30
Publication date: 2013-10-23
Anticipated expiration: 2032-03-30
Also published as: CN103369694B

Abstract

The invention provides a self-adaptive physical downlink control channel (PDCCH) format selecting method. The method comprises following steps. Firstly, a base station divides a value range of a channel quality indication CQ1 grade into multiple value intervals in advance and prescribes the PDCCH formats corresponding to value intervals. Then, the base station receives a CQ1 grade reported by UE and determines the value interval of the CQ1 grade. Finally, the base station transmits DCI information by using the PDCCH format corresponding to value interval.

Description

The system of selection of a kind of self adaptation PDCCH form

Technical field

The present invention relates to wireless communication technology field, relate in particular to the system of selection of a kind of self adaptation Physical Downlink Control Channel (PDCCH) form.

Background technology

LTE is a kind of accurate 4G system, and it can maximum as far as possible raising power system capacity, and the download service of uploading of better quality is provided.

For descending LTE system, comprise Physical Broadcast Channel (PBCH), Physical Control Format Indicator Channel (PCFICH), physical hybrid automatic repeat request indicator channel (PHICH), Physical Downlink Control Channel (PDCCH), Physical Downlink Shared Channel (PDSCH), wherein that the transmission rate related content mainly is PDCCH and PDSCH.The needed control information of these two channels carrying data receiver is such as resource distribution, modulation coding mode, redundancy versions etc.; A carry data information content, its correct reception can reflect into transmission rate.

The correct demodulation of PDSCH channel depends on the correct reception of PDCCH, and can't correctly receive the PDCCH channel just can not demodulation PDSCH channel.How to guarantee as far as possible the PDCCH Receiver Precision, become and improve the major issue that transmission rate need to be considered.

4 kinds of PDCCH forms are provided in the LTE standard, as shown in table 1:

The PDCCH form	The CCE number	Resource grains subgroup number	The PDCCH bit number
				0	1	9	72
1	2	18	144
				2	4	36	288
3	8	72	576

Table 1

The number of resources that the Downlink Control Information (DCI) of the different current transmission of PDCCH format determination uses represents with the form of CCE.In the LTE system, CCE is the used physical resource of control information transmission, is shared by uplink scheduling and descending scheduling.As shown in table 1, have four kinds of PDCCH forms, respectively corresponding 1/2/4/8 CCE.Each CCE is comprised of 9 resource grains subgroups (REG), and each REG comprises 4 resource particle (RE, Resource Element).When transmitting, PDCCH can select to be fit to according to four kinds of forms the CCE length bear control information of oneself.

The at present system of selection of PDCCH form mainly contains fixedly PDCCH form (fixation of C CE length) and according to the adaptively selected PDCCH form of DCI length (CCE length).

The PDCCH form system of selection of fixation of C CE length realizes simple, but can not be associated with the UE actual channel state, mainly has following shortcoming:

1) control information transmission and transfer of data are not mated;

Such as fixing PDCCH form 0, namely with 1 CCE bear control information, under the relatively poor condition of channel condition, because the control information resource is few, code check is high, receives the error rate high, even the PDSCH data can correctly receive under current channel condition, but owing to can't obtain correct control information, can only skip PDSCH and receive, causing like this current frame data transmitted bit number is 0;

2) resource overhead situation improperly;

Suppose fixedly PDCCH form 3, adopt 8 CCE bearing downlinks control information (DCI), at this moment the control information transmission code rate is very low, can guarantee good control channel receptivity, has taken a large amount of control channel resources but negative effect is each UE.Because control channel can use resource less, general control also will carry PCFICH and PHICH information simultaneously in 3 OFDM symbols, and the resource that can be used for the PDCCH channel just still less.So to take resource too much as the PDCCH of UE, each subframe support is done professional number of users and has just been tailed off, and especially in the situation that the CFI configuration is less, it is particularly evident that this situation embodies.And for channel condition preferably, correctly receiving PDCCH does not need code check too low, and it is exactly a kind of the waste under this condition that each PDCCH uses the expense of 8 CCE.

So fixedly the PDCCH form may cause some UE when bad channel conditions, select CCE length little; Perhaps when channel condition is better, select CCE length excessive; Cause the expense can not the current channel condition of fine coupling, restriction data transmission performance and overhead.

According to the adaptively selected CCE length of DCI length, with respect to fixation of C CE, certain improvement has been arranged, use different DCI forms for the UE different transmission mode, utilize the adaptive definite PDCCH form of DCI message length (CCE length), can guarantee that the control information transmission code rate is basicly stable, channel of living in is different but this scheme is not still considered different UEs, and the different channels state has a significant impact for the control information reception, so still has two shortcomings recited above.

Summary of the invention

The invention provides the system of selection of a kind of self adaptation PDCCH form, the CCE length that takies according to the selection control channel of Real-time Channel state self-adaption, thereby guarantee to be complementary with the PDSCH that relies on the PDCCH reception, have higher user performance and entire system performance.

A kind of self adaptation PDCCH form system of selection that the embodiment of the invention provides comprises the steps:

A, base station are divided into a plurality of intervals with the span of channel quality indicator (CQI) grade in advance, and stipulate the PDCCH form that each interval is corresponding;

B, base station receive the CQI grade that UE reports, and determine the residing interval of described CQI grade;

C, base station use PDCCH form corresponding to this interval to send DCI information.

Preferably, described steps A comprises: the base station arranges the first thresholding and the second thresholding, and wherein the first thresholding is greater than the second thresholding, if the CQI grade greater than the first thresholding, corresponding PDCCH form is PDCCH form 1; If the CQI grade is greater than the second thresholding and less than the first thresholding, corresponding PDCCH form is PDCCH form 2; If the CQI grade is less than the second thresholding, corresponding PDCCH form is PDCCH form 3.

Preferably, described base station arranges the first thresholding and the second thresholding comprises:

Close PDCCH, adopt the Adaptive Modulation and Coding mode to carry out the PDSCH transfer of data, and record CQI grade corresponding to each subframe;

All subframe CQI grades are averaged computing, thereby obtain the corresponding relation of each signal to noise ratio snr and CQI grade;

Fixedly the PDCCH form carries out down link emulation, obtains control information threshold level corresponding under the different PDCCH forms;

PDCCH threshold level under the more different CCE, and in conjunction with the corresponding relation of SNR and CQI grade, corresponding CQI grade when determining different CCE transmission under the DCI form of current transmission, corresponding CQI grade arranges described the first thresholding and the second thresholding during according to described different CCE transmission.

Obtain the demodulation performance of control channel under the different CCE length: the corresponding relation of SNR and BLER;

Determine SNR corresponding to various situation control channel demodulation thresholds;

Obtain the corresponding relation of SNR and CQI grade under the current transmission mode;

Determine the CQI grade that each demodulation threshold is corresponding;

Produce the first thresholding and the second thresholding that the PDCCH form is selected.

Preferably, the demodulation performance of control channel under the different CCE length of described acquisition: the corresponding relation of SNR and BLER comprises: build independently control channel chain channel platform, adopt respectively the mode of fixation of C CE length to carry out the control channel performance simulation, obtain under each CCE length, set corresponding relation between SNR and output BLER.

Preferably, described definite SNR corresponding to various situation control channel demodulation thresholds comprises:

According to actual conditions, corresponding SNR is demodulation threshold when determining the BLER fetching definite value of current control channel, can obtain the demodulation threshold that characterizes with SNR corresponding to each CCE length according to corresponding relation between the SNR that has obtained and output BLER.

Preferably, the span of the designated value of described BLER is 0.01 to 0.1.

Preferably, comprise before the CQI grade that the described base station reception of step B UE reports:

UE receives downstream signal, carries out the CRS channel estimating;

UE utilizes CRS to carry out the CQI rating calculation, obtains current CQI grade;

UE reports the CQI grade to the base station.

As can be seen from the above technical solutions, the corresponding relation of CQI span and PDCCH form is set, dynamically adjusts the PDCCH form according to current channel quality and send DCI, to mate current channel condition, be unlikely to occur the PDCCH transmission inharmonious with channel, cause systematic function to descend.The present invention can the optimization system expense, under the condition that guarantees the systematic function optimum, reduces as far as possible overhead, keeps simultaneously a plurality of UE to do business.Further, the present invention embodies channel status by the link performance analysis by the CQI class information, thereby has provided the method for the decision threshold calculating of definite CQI span, does not need to introduce new feedback information, does not increase overhead and realizes simple.

Description of drawings

Fig. 1 is self adaptation PDCCH form system of selection schematic flow sheet provided by the invention;

The method flow diagram of the decision threshold of a kind of definite CQI grade value that Fig. 2 provides for the embodiment of the invention;

The another kind that Fig. 3 embodiment of the invention provides is determined the method flow diagram of the decision threshold of CQI grade value.

Embodiment

The present invention program is the CCE length that the selection control channel according to the Real-time Channel state self-adaption takies, and guarantees and relies on the PDSCH that PDCCH receives and be complementary.In mobile communication system, can embody channel status by signal to noise ratio snr, SNR finally can embody by the CQI grade again.The basic thought of self adaptation PDCCH form provided by the invention system of selection is, the base station is divided into a plurality of intervals with the span of CQI grade in advance, and stipulates the PDCCH form that each interval is corresponding.The residing interval of CQI grade that UE reports is determined in the base station, uses PDCCH form corresponding to this interval to send DCI information.

Clearer for the know-why, characteristics and the technique effect that make technical solution of the present invention, below in conjunction with specific embodiment the present invention program is described in detail.

Figure 1 shows that self adaptation PDCCH form system of selection flow process provided by the invention, comprise the steps:

Step 101:UE receives downstream signal, carries out the CRS channel estimating.

Step 102:UE utilizes CRS to carry out the CQI rating calculation, obtains current CQI grade.

Step 103:UE reports the CQI grade to the base station.

Step 104: the base station receives the CQI grade that UE reports, and determines the residing interval of described CQI grade.

Step 105: the base station uses PDCCH form corresponding to this interval to send DCI information.

For making the present invention program reach comparatively desirable technique effect, its key is to determine the thresholding corresponding with channel status, according to the interval of this thresholding classifying rationally CQI grade.Fig. 2 shows the generation flow process of described thresholding, comprises the steps:

Step 201: close PDCCH, get rid of the impact that PDCCH receives PDSCH, adopt the Adaptive Modulation and Coding mode to carry out the PDSCH transfer of data, and record CQI grade corresponding to each subframe;

Step 202: each all subframe CQI grade of setting SNR is averaged computing, thereby obtains the corresponding relation (being denoted as SNR-CQI) of each SNR and average CQI grade;

Step 203: for each possible PDCCH form, fixedly PDCCH form (fixation of C CE length) carries out down link emulation, obtains control information threshold level (corresponding SNR represents with BLER=0.01) corresponding under the different PDCCH forms;

Step 204: the PDCCH threshold level under the more different CCE, and in conjunction with the corresponding relation of SNR and CQI, corresponding CQI grade when determining different CCE transmission under the DCI form of current transmission, corresponding CQI grade arranges decision threshold during according to described different CCE transmission.

Specifically, can obtain the corresponding relation of SNR and CQI grade according to step 201 and step 202, different CCE length are to deserved threshold level (SNR value) in the time of can being obtained transmitting DCI information by step 203, CQI rate range corresponding to different CCE length during according to SNR-CQI corresponding relation and the current DCI form of the definite transmission of SNR-CCE length corresponding relation, decision threshold corresponding in the time of different CCE length can being transmitted like this replaces the mode of SNR value to characterize with the CQI grade.

When the SNR numerical value among SNR among the SNR-CCE and the SNR-CQI does not wait, adopt the SNR value (such as the 8dB respective column among the upwards approximate SNR-CQI of 7dB among the SNR-CCE) of upwards getting among the approximate mode equivalence SNR-CQI.

Because optional PDCCH form has 4 kinds, if the unique corresponding PDCCH form of interval then can be divided at most 4 intervals.

The embodiment of the invention adopts two thresholdings that the span of CQI grade is divided into Three regions, and is specific as follows:

When the CQI grade greater than thresholding 1 (threshold1), illustrate that then current channel condition is better, can support the transmission of high code check, transmission can be used less control resource for PDCCH, selects PDCCH form 1;

When the CQI grade greater than thresholding 2 (threshold2) and less than thresholding 1, illustrate that then current channel condition is general, need slightly more control resources for PDCCH transmission, select PDCCH form 2;

When the CQI grade less than thresholding 2, illustrate that then current channel condition is relatively poor, need to reduce as far as possible transmission code rate, can use more control resource for PDCCH transmission, select PDCCH form 3.

Wherein, because the DCI length that general downlink transfer is used is longer, use 1CCE to carry out the PDCCH transmission, the control information error probability is higher, so, general recommendations avoids using the 1CCE transmission, namely avoid adopting PDCCH form 0 to send DCI information, unless channel condition is very good or the DCI message length hour, the effective information bit only has 15 (DCI Format 1 effective information 42 bits) when transmitting such as DCI Format 1C, at this moment under same channel conditions (SNR-CQI) can reduce a CCE length scale and transmit, and at this moment just might use 1CCE.

7,9,12dB take DCI form 1 as example, PDCCH demodulation threshold corresponding to different CCE transmission (corresponding SNR value during BLER=0.01, this value can adjust accordingly as required) is:;

For CQI grade corresponding to different channel status (weighing by SNR), as shown in table 2 is TM7 wave beam forming SNR and CQI grade corresponding relation:

Table 2

CCE length	1	2	4	8
					SNR(dB)	\	12	9	7

Table 3

For the TM7 beamforming transmission under precondition, Threshold1=12 is set, Threshold2=10 like this.

Each parameter of each thresholding of this programme is based on the empirical value that present simulated conditions and algorithm provide, if algorithm or other condition change, relevant threshold value also should be done corresponding adjustment.

The embodiment of the invention also provides the method for the decision threshold of another kind of definite CQI grade value, as shown in Figure 3, comprises the steps:

Step 301: the demodulation performance that obtains control channel under the different CCE length: the corresponding relation of SNR and BLER.

Build independently control channel chain channel platform, adopt respectively the mode of fixation of C CE length to carry out the control channel performance simulation, obtain under each CCE length, set corresponding relation between SNR and output BLER.This mode is only as example, and is not used in the present invention is limited.

Step 302: determine SNR corresponding to various situation control channel demodulation thresholds.

According to actual conditions, determine the performance index that current control channel will satisfy, namely BLER for how many times corresponding SNR be that demodulation threshold (is got the corresponding SNR of 0.01BLER when General Requirements is strict; Require to get when loose the corresponding SNR of 0.1BLER), can obtain the demodulation threshold that characterizes with SNR corresponding to each CCE length according to step 301 result.This mode is only as example, and is not used in the present invention is limited.

Step 303: the corresponding relation that obtains SNR and CQI grade under the current transmission mode.

Build independently Traffic Channel link simulation platform, think that control channel receives total correctness this moment, error code is all owing to the PDSCH transmission causes, can obtain like this setting SNR and output CQI grade corresponding relation (general SNR corresponding to CQI grade is spaced apart 2dB, thus emulation SNR is set should be to be not more than 2dB as the interval).This mode is only as example, and is not used in the present invention is limited.

Step 304: determine the CQI grade that each demodulation threshold is corresponding.

The SNR-CQI corresponding relation that the CCE length that obtains according to step 302-SNR corresponding relation and step 303 obtain can be set up CCE length and CQI grade corresponding relation; In order to guarantee that as far as possible control channel receives, above-mentioned corresponding relation has provided stricter thresholding and has selected, and SNR is at once taking the upwards principle of correspondence, such as the SNR=8dB among the corresponding SNR-CQI of 7dB among the SNR of control channel emulation and the SNR-CQI;

Step 305: produce the decision threshold that the PDCCH form is selected.

Determine final several decision gate limit values according to step 304, shown in table 2, table 3.

The present invention program has following advantage:

1) corresponding relation of CQI span and PDCCH form is set, dynamically adjusts the PDCCH form according to current channel quality and send DCI, to mate current channel condition, be unlikely to occur the PDCCH transmission inharmonious with channel, cause systematic function to descend;

2) be used for determining DCI transfer resource number by dynamically adjusting the PDCCH form, further the optimization system expense under the condition that guarantees the systematic function optimum, reduces overhead as far as possible, keeps simultaneously a plurality of UE to do business.

3) by the link performance analysis channel status is embodied by the CQI class information, thereby provided the method that above-mentioned decision threshold calculates, do not need to introduce new feedback information, do not increase overhead and realize simple.

The above only is preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of making, is equal to replacement, improvement etc., all should be included within the scope of protection of the invention.

Claims

1. self adaptation physical downlink control channel PDCCH form system of selection is characterized in that, comprises the steps:

2. method according to claim 1 is characterized in that, described steps A comprises: the base station arranges the first thresholding and the second thresholding, and wherein the first thresholding is greater than the second thresholding, if the CQI grade greater than the first thresholding, corresponding PDCCH form is PDCCH form 1; If the CQI grade is greater than the second thresholding and less than the first thresholding, corresponding PDCCH form is PDCCH form 2; If the CQI grade is less than the second thresholding, corresponding PDCCH form is PDCCH form 3.

3. method according to claim 2 is characterized in that, the first thresholding is set in described base station and the second thresholding comprises:

4. method according to claim 2 is characterized in that, the first thresholding is set in described base station and the second thresholding comprises:

Determine the CQI grade that each demodulation threshold is corresponding;

5. method according to claim 4, it is characterized in that, the demodulation performance of control channel under the different CCE length of described acquisition: the corresponding relation of SNR and BLER comprises: build independently control channel chain channel platform, adopt respectively the mode of fixation of C CE length to carry out the control channel performance simulation, obtain under each CCE length, set corresponding relation between SNR and output BLER.

6. method according to claim 5 is characterized in that, described definite SNR corresponding to various situation control channel demodulation thresholds comprises:

7. method according to claim 6 is characterized in that, the span of the designated value of described BLER is 0.01 to 0.1.

8. method according to claim 1 is characterized in that, comprises before the CQI grade that the described base station reception of step B UE reports:

UE receives downstream signal, carries out the CRS channel estimating;

UE reports the CQI grade to the base station.