CN103731236B - Blind detection method for physical downlink control channel - Google Patents

Abstract

The invention discloses a blind detection method for a physical downlink control channel. Due to the facts that the mode of combined blind detection is adopted, at least two lengths are adopted for rate matching removal, and the relations between indexes including a PDCCH detection threshold, the missing detection probability, the false detection probability, the average detection frequency and the maximum detection frequency are balanced, the PDCCH detection accuracy is overall improved, and the risk of PDCCH false detection is reduced.

Description

A method for blind detection of physical downlink control channel

technical field

The present application relates to the technical field of mobile communication, in particular to the Long Term Evolution (LTE, Long Term Evolution)/LTE-A system, and in particular to a method for blind detection of a Physical Downlink Control Channel (PDCCH, Physical Downlink Control Channel).

Background technique

The PDCCH in the 3GPP LTE/LTE-A system carries various types of downlink control information. The base station sends control information to the UE by allocating different time-frequency resources and using reasonable modulation and coding according to the actual channel conditions of the user equipment (UE). The UE usually does not know the number of control channel elements (CCE, Control Channel Elements) occupied by the current PDCCH, what format information of the downlink control information (DCI, Downlink Control Information) is transmitted, and does not know where the information it needs is located. But the UE knows what information it is currently expecting. For example, the information that the UE expects in the idle (Idle) state is paging, SI; after initiating random access, it expects a random access channel (RACH) response, and there is uplink data waiting to be sent Time to look forward to ULGrant et al. For different expected information, the UE uses the corresponding radio network temporary identifier (RNTI) to check the cyclic redundancy check code (CRC, Cyclic Redundancy Check) with the CCE information. If the CRC check is successful, then the UE knows that the information is If you need it, you can further know the corresponding DCI format and modulation method, so as to decode the DCI content. This is the so-called blind detection process.

If the UE searches in the order of CCEs, the amount of calculation on the UE side is considerable, especially for systems with relatively large bandwidth and a large number of CCEs. Therefore, the efficiency of blind detection depends on the data processing capacity of the system and Response time and other characteristics have a great relationship, the higher the efficiency of blind detection, the better the system performance. The UE receives downlink control information through PDCCH blind detection (different CCE sets, different search spaces, and as few detection times as possible in the statistical sense). It is necessary to prevent various DCI false detections and ensure a reasonable detection threshold. Reduce the probability of missed detection.

In the prior art, the PDCCH blind detection process includes:

Step 101: In each downlink subframe, the UE detects the OFDM symbols in the control region, performs demapping, demodulation and descrambling on the PDCCH channel, and the descrambled data is used as input data for blind detection.

Step 102: Calculate the current search starting position.

Step 103: Read the CCEs at the starting position of the corresponding search space according to the CCE set level L, perform rate matching and Viterbi decoding on the read data, and then perform RNTI descrambling and CRC on the obtained data check.

Step 104: If the verification is successful, receive the data and end this process; otherwise, give up this search and continue to execute step 105;

Step 105: Determine whether all candidate PDCCHs in the current space have been searched, if not, add L to the search start position, and return to step 103 for the next search; if yes, execute step 106.

Step 106: Determine whether the blind inspection of all aggregation levels is completed, if yes, the blind inspection ends, otherwise, enter the next aggregation level and return to step 102.

The PDCCH blind detection process in the prior art has the following disadvantages:

(1) False detection probability of different RNTI descrambling. For example, if the base station sends a DCI to a certain user, due to channel changes and noise interference, other users may use different RNTI blind detections, and the CRC check may be correct.

(2) The false detection probability introduced by DCI solution rate matching of different lengths. For example, if a base station sends a DCI to a certain user, due to channel changes and noise interference, the user’s blind detection may resolve multiple DCIs of different lengths, and the CRC Calibration is correct.

(3) Misjudgment probability of 16bit CRC check in low signal-to-noise ratio environment. For example, due to channel changes and noise interference for a user, the blind check result may also be correct, and the DCI not sent by the base station can be analyzed .

Contents of the invention

The present application provides a method for blind detection of a physical downlink control channel, which can reduce the probability of false detection.

A method for blind detection of a physical downlink control channel provided in an embodiment of the present application includes:

Read CCEs at the starting position of the corresponding search space according to the control channel element CCE set level L;

Use the first length to perform rate matching on the read data, Viterbi decoding, and then descramble the data obtained by wireless network temporary identification RNTI and cyclic redundancy check code CRC check, wherein the downlink obtained after RNTI descrambling The control information DCI is called the first DCI, and the obtained CRC check is called the first CRC check;

If the first CRC check is wrong, it is considered that the check fails and the process ends; otherwise, the second length is further used to perform derate matching on the read data, Viterbi decoding, and then perform RNTI descrambling and CRC on the obtained data Checking, wherein the downlink control information DCI obtained after RNTI descrambling is called the second DCI, and the obtained CRC check is called the second CRC check;

If the second CRC check is wrong, consider the check failed and end this process; otherwise, further judge whether the first DCI and the second DCI are the same; if the first DCI and the second DCI are different, consider the check failed and end this process process; if they are the same, it is considered that the verification is successful, the data is received and the process ends.

Preferably, the first length is the default solution rate matching length L _x corresponding to the CCE aggregation level L, and according to the aggregation level L=1/2/4/8, corresponding to the default length L _x =72/144/288/ 576.

Preferably, the second length is the adaptive solution rate matching length L _y , and the value range of the adaptive length L _y is [(L _dci +16), L _x ], where L _dci is the current blind detection DCI length , L _x is the default solution rate matching length corresponding to the current CCE set level L.

Preferably, the adaptive length L _y is a determined value within the value range [(L _dci +16), L _x ].

Preferably, the adaptive length L _y is a variable value within a value range.

Preferably, the adaptive length L _y changes as the UE measures the signal-to-noise ratio SNR, and its law is: decrease as the SNR increases until the minimum value (L _dci +16); increase as the SNR decreases until Maximum L _x .

From the above technical solutions, it can be seen that if the final CRC check of the default length solution rate matching or adaptive length solution rate matching fails, the check is considered to be a failure; and even if both CRC checks are successful, it is necessary to verify both Whether the DCI is the same, only when the DCI is the same, the verification is considered successful. Compared with the conventional PDCCH blind detection process in the prior art, the average number of detections will increase by one time, and the probability of false detection will be greatly improved. At the same time, due to Combined blind detection has stricter requirements than conventional blind detection, which is conducive to improving the correct rate of PDCCH detection and reducing the risk of PDCCH false detection.

Description of drawings

FIG. 1 is a schematic diagram of a PDCCH blind detection process in the prior art;

FIG. 2 is a schematic diagram of a PDCCH blind detection process provided by an embodiment of the present application.

detailed description

This application aims at the problems existing in the existing PDCCH blind detection process. By combining blind detection, at least two lengths are used for solution rate matching, and by balancing the PDCCH detection threshold, missed detection probability, false detection probability, average detection times and maximum detection The relationship between indicators such as the number of times improves the PDCCH detection accuracy rate on the whole and reduces the risk of PDCCH false detection.

In order to make the technical principles, features and technical effects of the technical solution of the present application clearer, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

The technical solution of the present application is mainly aimed at improving step 103 in the PDCCH blind detection process of the prior art shown in Figure 1, and the improved step 103 is shown in Figure 2, including the following steps:

Step 103-1: Read the CCEs at the starting position of the corresponding search space according to the CCE set level L.

Step 103-2: Use the first length to perform derate matching on the read data, Viterbi decoding, and then perform wireless network temporary identifier RNTI descrambling and cyclic redundancy check code CRC check on the obtained data, wherein RNTI descrambling The downlink control information DCI obtained after scrambling is called the first DCI, and the obtained CRC check is called the first CRC check.

Step 103-3: Determine whether the first CRC check is correct, if yes, execute step 103-4, otherwise consider the check failed, go to step 105.

Step 103-4: Use the second length to perform derate matching on the read data, Viterbi decoding, and then perform RNTI descrambling and CRC check on the obtained data, wherein the downlink control information DCI obtained after RNTI descrambling is called For the second DCI, the obtained CRC check is called the second CRC check.

Step 103-5: Determine whether the second CRC check is correct, if yes, execute step 103-6, otherwise consider the check failed, go to step 105.

Step 103-6: Determine whether the first DCI and the second DCI are the same, if yes, perform step 103-7; otherwise, consider the verification failed and go to step 105.

Step 103-7: If the verification is considered successful, the data is received and this process ends.

Preferably, the first length is the default solution rate matching length L _x corresponding to the CCE aggregation level L, which corresponds to the default length L _x =72/144/288/576 respectively according to the aggregation level L=1/2/4/8.

Preferably, the second length is the adaptive solution rate matching length L _y , and the value range of the adaptive length L _y is [(L _dci +16), L _x ], wherein L _dci is the current blind detection DCI length, L _x is the default solution rate matching length corresponding to the current CCE set level L.

The embodiment of the present application provides several methods for determining _Ly :

(1) The adaptive length L _y is a certain value within the value range [(L _dci +16), L _x ], and the certain value can be configured as the maximum value L _x , or as the minimum value (L _dci +16), Or configure to other intermediate values. For example, the following formula can be used to determine the value of L _y : L _y ={(L _dci +16)+(L _x )}/2;

(2) The adaptive length L _y is a variable value within the value range, which changes with the change of UE measurement signal-to-noise ratio _SNR . ); increases with decreasing SNR up to a maximum value of L _x .

The above two methods are only used as examples, and are not intended to limit the technical solution of the present application.

It can be seen from the above process that if the final CRC check of the default length solution rate matching or adaptive length solution rate matching fails, the check is considered to be a failure; Whether the DCIs are the same, the verification is considered successful only when the DCIs are the same, thereby avoiding false detections caused by accidental CRC errors.

The above descriptions are only preferred embodiments of the application, and are not intended to limit the scope of protection of the application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the technical solutions of the application are It should be included within the protection scope of this application.

Claims (4)

1. a kind of method of Physical Downlink Control Channel blind check is it is characterised in that include:

Cces is read according to the original position in corresponding search space for the control channel element cce set class l；

Using the first length, the data reading is carried out solving rate-matched, viterbi decodes, then will obtain data again and carry out no Line Network Temporary Identifier rnti descrambling and CRC crc verification, the descending control letter obtaining after wherein rnti descrambling Breath dci is referred to as a dci, crc verification the referred to as the crc verification obtaining；

If crc check errors are then it is assumed that verify unsuccessfully and process ends；Otherwise, adopt the second length further to reading The data taking carries out solving rate-matched, and viterbi decodes, and then will obtain data again and carry out rnti descrambling and crc verification, wherein The Downlink Control Information dci obtaining after rnti descrambling is referred to as the 2nd dci, crc verification the referred to as the 2nd crc verification obtaining；

If the 2nd crc check errors are then it is assumed that verify unsuccessfully and process ends；Otherwise, determine whether a dci and second Whether dci is identical；If a dci and the 2nd dci different then it is assumed that verify unsuccessfully simultaneously process ends；If identical then it is assumed that school Test successfully, receiving data process ends；

Described first length is cce set class l corresponding acquiescence solution rate-matched length l_x, according to set class l=1/2/4/ 8, correspond to default-length l respectively_x=72/144/288/576；

Described second length is adaptive de rate-matched length l_y, adaptive-length l_ySpan be [(l_dci+16), l_x], wherein l_dciFor current blind check dci length, l_xFor current cce set class l corresponding acquiescence solution rate-matched length.

2. method according to claim 1 is it is characterised in that adaptive-length l_yFor span [(l_dci+16),l_x] in Determination value.

3. method according to claim 1 is it is characterised in that adaptive-length l_yFor meeting the variable value in span.

4. method according to claim 3 is it is characterised in that adaptive-length l_yChange with ue measurement signal to noise ratio snr change Become, its rule is: raise with snr and reduce, until minima (l_dci+16)；Reduce with snr and increase, until maximum l_x.