WO2011036986A1

WO2011036986A1 - Cross-carrier indication method and user equipment

Info

Publication number: WO2011036986A1
Application number: PCT/JP2010/064974
Authority: WO
Inventors: Zeng YANG; Renmao Liu; Ming Ding; Yingyu Zhang; Yongming Liang
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2009-09-28
Filing date: 2010-08-26
Publication date: 2011-03-31
Also published as: CN102036314B; CN102036314A

Abstract

The present invention discloses a method for performing cross-carrier indication and corresponding user equipment. The method comprises steps of detecting a PCFICH on a first carrier carrying a PDCCH and acquiring control information symbol number information on the first carrier; detecting the PDCCH on the first carrier and acquiring PDSCH resource block assignment information, carrier indicator and HARQ information according to the control information symbol number information on the first carrier; detecting control information symbol number information on a second carrier carrying a PDSCH indicated by the acquired carrier indicator; and acquiring or not acquiring the PDSCH according to the acquired control information symbol number information on the second carrier and/or the PDSCH resource block assignment information. This method can detect PCFICH errors on a carrier carrying the PDSCH, or improve detection performance for the PCFICH of the carrier, or avoid detection errors for the PCFICH of the carrier so as to be able to solve the HARQ buffer corruption problem caused by PCFICH detection errors.

Description

DESCRIPTION

TITLE OF INVENTION

CROSS-CARRIER INDICATION METHOD AND USER

EQUIPMENT

TECHNICAL FIELD

The present invention relates generally to mobile communication technique fields . More specifically, the present invention relates to a cross-carrier indication processing in LTE-Advanced (Long Term Evolution-Advanced) and 4G system. The present invention proposes a cross- carrier indication method and a corresponding user equipment.

BACKGROUND ART

3GPP (3rd Generation Partnership Project) has determined in RAN l #53bis Meeting that a downlink bandwidth of LTE-Advanced system will adopt Carrier Aggregation technologies which may support a system bandwidth larger than 20MHz. This brings more flexibility to designs of downlink control channels, while bringing new challenges.

After discussion in 3GPP TSG RAN I No .58 Meeting, two kinds of optional downlink control channel structures are reserved for the LTE-Advanced system (See : Way Forward on PDCCH for Bandwidth Extension in LTE-A, R l -093699 , RAN 1 #58, Alcatel-Lucent et. al. , August 2009) . In the first kind of structure, PDCCH (Physical Downlink Control Channel) on a certain carrier is only used to indicate resource assignment information of the carrier that it belongs to . In the second kind of structure, PDCCH on a certain carrier can be used to indicate resource assignment information of the carrier that it belongs to and that of other carriers. As illustrated detailedly in Fig. l , in an intra-carrier indication structure of PDCCH option l a, PDCCH is used to indicate PDSCH (Physical Downlink Share Channel) assignment information of the carrier that it belongs to . In a cross-carrier indication structure of PDCCH option l b, PDCCH on carrier # 1 can be used to indicate not only the PDSCH assignment information on the carrier (carrier # 1 ) that it belongs to but also PDSCH assignment information on another carrier (carrier #2) .

The above PDCCH options l a and l b for the downlink control channel indication structure each have their advantages and disadvantages. The PDCCH option l a is fully compatible with LTE Release 8 structure . The PDCCH option l b can not realize full backward compatibility, but has following advantages in comparison with option l a in view of supporting new characteristics of LTE-Advanced:

enhanced PDCCH intra-cell interference control especially in a heterogeneous network,

more scheduling flexibility,

effective PUCCH (Physical Uplink Control Channel) utilization,

capability of supporting a carrier aggregation scenario in which there are more uplink carriers than downlink carriers, and

capability of supporting carriers without PDCCH .

However, in implementations the option l b needs to solve an important problem of HARQ (Hybrid Automatic Request) buffer corruption caused by PCFICH (Physical Format Indication Channel) detection error (See: Issues on Cross-Carrier PDCCH Indication for Carrier Aggregation, R l - 093047, 3GPP RAN 1 #58, Huawei, August 2009) . Reasons of this problem are illustrated in Figure 2. For the PDCCH option l a, correct PDSCH reception can be realized only when PCFICH and PDCCH corresponding to the PDSCH are both correct. Thus, PDCCH detection performs an additional check for PCFICH in an implicit manner and PDCCH detection error (misdetection) will directly lead to non-reception of PDSCH and thus will not affect subsequent HARQ processes. In short, there is no direct relationship between PCFICH detection and PDSCH reception. For the PDCCH option l b, if PCFICH detection error occurs on a carrier carrying the PDSCH (there is no corresponding PDCCH on the carrier) , a user equipment is unable to acquire a correct PDSCH starting location, resulting that the user equipment stores incorrect data in the HARQ buffer and feedbacks NACK and ultimately subsequent HARQ combing can not obtain correct result all along. In other words, correct PDSCH decoding on the carrier carrying the PDSCH relates to three factors: correct PCFICH detection on the carrier carrying the PDCCH, correct detection of PDCCH corresponding to the PDSCH on the carrier carrying PDCCH and correct PCFICH detection on the carrier carrying the PDSCH . The excessive requirement of correct PCFICH detection on the carrier carrying the PDSCH establishes direct relationship between the PCFICH detection and PDSCH reception. Ineffective subsequent HARQ retransmission caused by the PCFICH detection error on the carrier carrying the PDSCH will bring about utilization waste on system resources and will affect some traffics sensitive to packet loss rate, thus this problem needs to be settled. A research makes clear that reducing PCFICH detection error probability on the carrier carrying the PDSCH to l e ⁴ will help to mitigate negative impact from this problem.

Other literatures proposed some methods to solve this problem. One literature (See : Control Signaling Design for Supporting Carrier Aggregation, R l -090792 , 3GPP RAN 1 #56, Motorola, February 2009) proposes that information indicating a data transport block starting location can be inserted into resource assignment information of each carrier. In another simple method (See: Views on PDCCH Carrier Indicator, R l -093225, 3GPP RAN I #58, NEC Group, August 2009) , a cross-carrier scheduling user equipment sets the number of control information symbols on the carrier carrying PDSCH to be a fixed number, 3. This method will lead to large control information overhead in a case of the number of cross-carrier scheduling user equipments or allocated resource blocks being large and thus it is not a high-effective solution. Another method (See: PDSCH-to-RE mapping robust against CCFI reception errors, R l -081228, 3GPP RAN I #52bis, Samsung, March 2008) revises mapping from PDSCH to RE (Resource Element) such that modulated OFDM (Orthogonal Frequency Division Multiplexing) symbols on the PDSCH are firstly mapped in a time increasing order in Area 1 (i. e. , from the 4^th OFDM symbol to the 14^th OFDM symbol) and then are mapped in a time decreasing order in Area 2 (i. e. , from the 3^rd OFDM symbol to the 1 ^st OFDM symbol) . This method can guarantee correctness of the PDSCH starting location, however, when the PCFICH detection error occurs, decoding for code blocks in tail part of the PDSCH will be severely affected and correct reception of the whole transport block will be directly threatened.

The present invention provides a flexible, simple and high effective solution aiming at HARQ buffer corruption caused by the PCFICH detection error.

SUMMARY OF INVENTION

A technical problem to be solved by the present invention is how to solve an HARQ buffer corruption problem caused by PCFICH detection errors existing in cross-carrier indication in a scenario which needs to support the cross- carrier indication so as to improve system performance in a wireless communication system adopting component aggregation technologies and meanwhile how to maintain low overhead. The present invention aims to solve this problem and thus provides present technical solution so that the cross-carrier indication can be flexibly achieved in a wideband mobile communication system adopting the component aggregation technology.

According to a first aspect of the present invention, a method for cross-carrier indication is provided. This method comprises detecting a PCFICH (physical format indication channel) on a first carrier carrying a PDCCH (physical downlink control channel) and acquiring control information symbol number information on the first carrier; detecting the PDCCH on the first carrier and acquiring a PDSCH (physical downlink share channel) resource block assignment information, carrier indicator and HARQ (hybrid automatic request) information according to the control information symbol number information on the first carrier; detecting control information symbol number information on a second carrier carrying the PDSCH indicated by the acquired carrier indicator; and acquiring or not acquiring PDSCH according to the acquired control information symbol number information on the second carrier and/or the PDSCH resource block assignment information.

Preferably, the step of detecting the control information symbol number information on the second carrier comprises detecting a carrier indicator field in the acquired carrier indicator and acquiring the control information symbol number information on the second carrier. A length of the carrier indicator field is fixed to be three bits, and two redundancy bits in the carrier indicator field are used to indicate the control information symbol number information on the second carrier when system bandwidth is less than or equal to two carriers. Alternatively, the step of detecting the control information symbol number information on the second carrier comprises detecting a CRC (cyclic redundancy check) mask corresponding to the PDCCH carried by the first carrier and acquiring the control information symbol number information on the second carrier, wherein the CRC mask is obtained by adding a mask relative to the control information symbol number information on the second carrier to a CRC, in DCI (downlink control information) format, corresponding to the PDCCH carried by the first carrier. Here, the step of acquiring or not acquiring the PDSCH comprises acquiring the PDSCH according to the acquired control information symbol number information on the second carrier and the PDSCH resource block assignment information. More preferably, the present method further comprises placing the acquired PDSCH into an HARQ soft buffer according to the acquired HARQ information.

Preferably, the step of detecting the control information symbol number information on the second carrier comprises: detecting the PCFICH on the second carrier and acquiring the control information symbol number information indicated by the PCFICH as a PCFICH detection result, determining a location of a reserved resource and acquiring the reserved resource from the determined location according to the PCFICH detection result, and comparing contents in the reserved resource with pre-specified contents, wherein the location of the reserved resource is relative to the control information symbol number information on the second carrier and the contents of the reserved resource are pre-specified between a base station and a user equipment. Here , the step of acquiring or not acquiring the PDSCH comprises: acquiring the PDSCH according to the control information symbol number information indicated by the PCFICH if the contents are the same, and not acquiring the PDSCH if the contents are different. More preferably, the present method further includes after acquiring the PDSCH, placing the acquired PDSCH into an HARQ soft buffer according to the acquired HARQ information.

Preferably, the step of detecting the control information symbol number information on the second carrier comprises: jointly detecting PCFICH on the second carrier and a reserved resource extracted from a pre-specified location, and determining the control information symbol number information on the second carrier according to the joint detection result, wherein the location of the reserved resource is relative to the control information symbol number information on the second carrier and the location of the reserved resource is pre- specified between a base station and a user equipment. Contents of the reserved resource are obtained by coding the control information symbol number information on the second carrier. The step of acquiring or not acquiring PDSCH comprises acquiring the PDSCH according to the determined control information symbol number information and the PDSCH resource block assignment information. More preferably, the present method further includes placing the acquired PDSCH into an HARQ soft buffer according to the acquired HARQ information.

Preferably, the reserved resource is a resource reserved in a control region or a data region of the second carrier. The reserved resource is resource elements or control channel elements in the control region of the second carrier, or the reserved resource is resource elements in the data region of the second carrier or resource elements in the PDSCH allocated by a user equipment. More preferably, a temporal location of the reserved resource is the fourth OFDM (orthogonal frequency division multiplexing) symbol in a sub- frame and a frequency density is that each resource block has one resource element.

According to another aspect of the present invention, a user equipment capable of cross-carrier indication is provided. The user equipment comprises a first carrier PCFICH (physical format indication channel) detection unit configured to detect a PCFICH on a first carrier carrying a PDCCH (physical downlink control channel) and acquiring control information symbol number information on the first carrier, a PDCCH detection unit configured to detect the PDCCH on the first carrier and acquire a PDSCH (physical downlink share channel) resource block assignment information, carrier indicator and HARQ (hybrid automatic request) information according to the control information symbol number information on the first carrier, a second carrier control information symbol number information detection unit configured to detect control information symbol number information on a second carrier carrying the PDSCH indicated by the acquired carrier indicator, and a PDSCH acquisition unit configured to acquire or not acquire the PDSCH according to the acquired control information symbol number information on the second carrier and/ or the PDSCH resource block assignment information.

Preferably, the second carrier control information symbol number information detection unit detects a carrier indicator field in the acquired carrier indicator and acquires the control information symbol number information on the second carrier. Preferably, the second carrier control information symbol number information detection unit detects a CRC (cyclic redundancy check) mask corresponding to the PDCCH carried by the first carrier and acquires the control information symbol number information on the second carrier, wherein the CRC mask is obtained by adding a mask relative to the control information symbol number information on the second carrier to a CRC, in DCI (downlink control information) format, corresponding to the PDCCH carried by the first carrier. The PDSCH acquisition unit acquires the PDSCH according to the acquired control information symbol number information on the second carrier and the PDSCH resource block assignment information. More preferably, the user equipment further includes a PDSCH buffer unit configured to place the acquired PDSCH into an HARQ soft buffer according to the acquired HARQ information.

Preferably, the second carrier control information symbol number information detection unit comprises: a second carrier PCFICH detection unit configured to detect the PCFICH on the second carrier and acquire the control information symbol number information indicated by the PCFICH as a PCFICH detection result, a reserved resource detection unit configured to determine a location of reserved resource and acquire the reserved resource from the determined location according to the PCFICH detection result, and a comparison unit configured to compare contents in the reserved resource with pre-specified contents, wherein the location of the reserved resource is relative to the control information symbol number information on the second carrier and the contents of the reserved resource are pre-specified between a base station and a user equipment. The PDSCH acquisition unit acquires the PDSCH according to the control information symbol number information indicated by the PCFICH if the contents compared by the comparison unit are the same, and does not acquire the PDSCH if the contents are different. More preferably, the user equipment further includes a PDSCH buffer unit that places the PDSCH acquired by the PDSCH acquisition unit into an HARQ soft buffer according to the acquired HARQ information.

Preferably, the second carrier control information symbol number information detection unit comprises: a joint detection unit configured to jointly detect the PCFICH on the second carrier and a reserved resource extracted from a pre- specified location, and a decision unit configured to determine the control information symbol number information on the second carrier according to the j oint detection result, wherein the location of the reserved resource is relative to the control information symbol number information on the second carrier and the location of the reserved resource is pre- specified between a base station and the user equipment. The PDSCH acquisition unit acquires the PDSCH according to the determined control information symbol number information and the PDSCH resource block assignment information. More preferably, the user equipment further includes a PDSCH buffer unit that places the PDSCH acquired by the PDSCH acquisition unit into an HARQ soft buffer according to the acquired HARQ information.

According to the present invention, the HARQ buffer corruption caused by PCFICH detection error is considered and a cross-carrier indication method and corresponding user equipment are provided. The present scheme is simple and guarantees high efficient work of the system. In the present invention, starting with a carrier carrying PDSCH, PCFICH detection error of the carrier can be detected or PCFICH detection performance of the carrier can be improved according to cross-carrier indication by reserving control information or data resource symbols. Alternatively, starting with a carrier carrying PDCCH , PCFICH detection error on the carrier carrying PDSCH can be avoided by performing mask operation for the CRC in DCI format, which corresponds to the PDCCH on the carrier or adding additional information in the carrier indicator field of the PDCCH on the carrier. Therefore, the problem of HARQ buffer corruption caused by the PCFICH detection error can be solved.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.

Fig. 1 is a schematic diagram illustrating PDCCH structures option l a (intra-carrier indication) and option l b (cross-carrier indication) in an LTE-Advanced system.

Fig. 2 is a schematic drawing illustrating an HARQ buffer corruption problem caused by a PCFICH detection error.

Fig. 3 is a schematic drawing illustrating a PDCCH cross-carrier indication. Fig. 4 is a flowchart illustrating a PDCCH cross-carrier indication mechanism in LTE-A system without consideration of solving the problem of HARQ buffer corruption caused by PCFICH error.

Fig. 5 is a schematic drawing illustrating a reserved resource control region for solving the PCFICH error problem;

Fig. 6 is a flowchart illustrating processes of PCFICH error detection with use of the reserved resource control region;

Fig. 7 is a flowchart illustrating processes of improving PCFICH detection performance with use of the reserved resource control region;

Fig. 8 is a schematic drawing illustrating a reserved resource in a data region for solving the PCFICH error problem;

Fig. 9 is a flowchart illustrating processes of reserving partial resources of PDSCH of the user equipment for solving the PCFICH error problem;

Fig. 10 is a schematic drawing illustrating solving the PCFICH error problem by adding masking to CRC , in a DCI format, corresponding to PDCCH ;

Fig. 1 1 is a flowchart illustrating processes of solving the PCFICH error problem by adding masking to CRC, in a DCI format, corresponding to PDCCH;

Fig. 12 is a flowchart illustrating processes of solving the PCFICH error problem by adding control information symbol number information of the carrier carrying the PDSCH in a carrier indicator field;

Fig. 13 is a schematic drawing illustrating a user equipment structure configuration;

Fig. 14a is a schematic drawing illustrating of a second carrier control information symbol number detection unit of the user equipment according to the present invention; and Fig. 14b is a schematic drawing illustrating of a second carrier control information symbol number detection unit of the user equipment according to the present invention.

DESCRIPTION OF EMBODIMENTS

In order to clearly clarify implementing steps of the present invention, embodiments applicable to wireless communication systems supporting carrier aggregation technologies, especially LTE-Advanced cellular mobile communication system, according to the present invention are presented in the following descriptions. It is to be noted that the present invention is not limited to the following descriptions, but is also applicable to other relative wireless communication system.

Preferred embodiments will be explained by referring to the accompanying drawings. Unnecessary parts and functions for the present invention will be omitted for brevity so as to avoid confusion in understanding.

PDCCH indication mechanism referred to in the present invention will be briefly described before descriptions of an embodiment of the present invention. In LTE, since the system bandwidth consists of one carrier, a base station indicates whether there is downlink data of a specified user equipment in current sub-frame through DL assignment transferred by PDCCH of this carrier and provides corresponding HARQ information. The user equipment firstly detects PCFICH (Physical Format Indication Channel) in the current sub-frame so as to acquire the number of control information symbols in the current sub-frame; then blindly decodes a PDCCH in a control region indicated by the PCFICH according to RNTI (Radio Network Temporary Identifier) ; if detecting correct PDCCH relative to downlink assignments, acquires PDSCH resource block assignment information and HARQ information from the PDCCH; and finally extracts the PDSCH from the next OFDM symbol in the acquired control region according to the acquired PDSCH resource block assignment information and places it into an HARQ soft buffer.

As illustrated in Fig.3 , in the LTE-A system, the system bandwidth can consist of a plurality of carriers (Fig.3 illustrates an example of two carriers) . Thus, a plurality of system carriers can be allocated to the LTE-A user equipment simultaneously for data transportation. The PDCCH cross- carrier indication structure in the LTE-A system allows a PDCCH on a carrier to be used for indicating PDSCH assignment information on another carrier. Fig. 4 illustrates detailed procedures of PDCCH cross-carrier indication mechanism at the user equipment side in LTE-A system, which does not consider solving the problem of HARQ buffer corruption caused by PCFICH errors.

Step 401 : the user equipment detects the PCFICH on a carrier carrying the PDCCH in the current sub-frame and acquires the number of control information symbols on the carrier in the current sub-frame.

Step 402 : the user equipment blindly detects the PDCCH with the RNTI in a control region on the carrier in the sub- frame.

Step 403 : if detecting correct PDCCH which is relative to the downlink assignment and includes a non-null carrier indicator field, the user equipment acquires PDSCH resource block assignment information, carrier indicator and HARQ information from the PDCCH .

Step 404 : the user equipment detects the PCFICH on the carrier carrying the PDSCH, which is indicated by the carrier indicator, and acquires the number of control information symbols on the carrier in the current sub-frame .

Step 405 : the user equipment extracts the PDSCH from the next OFDM symbol in the control region on the acquired carrier in the current sub-frame according to the acquired PDSCH resource block assignment information and the number of control information symbols on the carrier in the current sub-frame.

Step 406: the user equipment places the PDSCH into the HARQ soft buffer according to the acquired HARQ information.

Embodiment l a:

As illustrated in Fig.5, a few REs (Resource Element) or a few CCEs (Control Channel Element) are reserved in the control region on the carrier carrying the PDSCH . Locations of these reserved resources are relative to the number of control information symbols indicated by the PCFICH and contents can be a sequence with a certain length and can be specified between the base station and the user equipment in advance.

Coding and modulation scheme can be same as that of CCE where the reserved resources locate. Therefore, the detection result of the PCFICH on the carrier carrying the PDSCH can be further confirmed with these reserved resources such that a detection accuracy of the PCFICH can be improved.

A PDCCH cross-carrier indication mechanism in the LTE-A system adopting this method is illustrated in Fig. 6.

Steps 60 1 -604 are the same as steps 40 1 -404 and steps 606-607 are the same as steps 405-406. Steps 605 and 608 different from Fig.4 are only described here . Step 605 : the user equipment determines locations of reserved resources according to the PCFICH detection result, and compares contents extracted from the reserved resources with pre-specified contents. If they are the same, which means correct, then the procedure proceeds to step 606.

Step 608 : if the result of Step 605 is different, which means error, the user equipment will deem that the base station has not transmitted any data and thus the user equipment will not feedback ACK/ NACK. Such situation corresponds to DTX (discontinuous transmission) of the user equipment, and the base station will detect the DTX later and take corresponding processing.

Embodiment l b:

A few REs (Resource Element) or a few CCEs (Control Channel Element) are reserved in the predetermined locations in the control region on the carrier carrying the PDSCH as the embodiment l a. The difference is that predetermined locations of these resources can be pre-specified between the base station and the user equipment and the number of control information symbols indicated by the PCFICH is encoded according to methods specified in section 5.3.4. 1 in 3GPP specification (TS 36.2 12 V8.7.0, "Evolved Universal Terrestrial Radio Access (E-UTRA) ; Multiplexing and channel coding") so as to obtain contents included in the reserved resources. For example, a coding manner of the contents can be same as that of the PCFICH . This operation does not change the original PCFICH . The user equipment performs joint detection for the contents in the PCFICH and reserved resources at the time of reception, for example, performing joint decoding for the contents in the PCFICH and reserved resources, respectively obtaining the number of control information symbols represented by the PCFICH and reserved resources and determining the correct number of the control information symbols therefrom, so as to improve the detection accuracy of the PCFICH .

A PDCCH cross-carrier indication mechanism in the LTE-A system adopting this method is illustrated in Fig. 7.

Steps 701 -704 are the same as steps 40 1 -403 and steps 705-706 are the same as steps 405-406. Step 704 different from Fig.4 is only described here .

Step 704 : the user equipment performs joint detection for the contents extracted from the resources in the reserved locations and the PCFICH and then the procedure proceeds to Step 705.

In embodiments l a and l b, if the reserved resource is

RE, then the control channel structure in 3GPP LTE needs to be redesigned. If the reserved resource is CCE, backward compatibility with the 3GPP LTE can be maintained .

Embodiment l c :

As shown in Fig.8, the present embodiment is the same as embodiments l a and l b in an aspect of reserved resource idea, but is different from them in that reserved resources locate in specified locations in a data region of a carrier carrying the PDSCH . The concrete location can be related to or not related to the number of the control information symbols indicated by the PCFICH . For example, a temporal location can be set as the fourth OFDM symbol in current sub-frame and frequency-domain locations can be as distributive as possible among frequency-domain sub-carriers of the symbol, for example, each resource block assigns one resource element. Note that a reference signal Port 5 originally used for multi-user MIMO (Multiple Input Multiple Output) shall be avoided. One method is to perform mapping according to a method defined in section 6. 10.3.2 in 3GPP specification (TS 36.2 1 1 V8.7.0 , "Evolved Universal Terrestrial Radio Access (E-UTRA) ; Physical Channels and Modulation") , but a utilized cell frequency shift chooses a value different from the Port 5 reference signal . Contents of the reserved resource can be similar to those in Embodiments l a and l b and can adopt a pre-specified sequence or control symbol number information which is encoded with the same coding manner as that of the PCFICH .

Procedures of the PDCCH cross-carrier indication mechanism in the LTE-A system adopting this method are the same as those illustrated in Fig. 6 and Fig. 7. In embodiment l c, for an LTE user, data symbols corresponding to the reserved resource location need to be punctured when the base station transmits signals. For an LTE-A user, it can choose to puncture or not puncture . If choosing to not puncture, affection of the reserved resources shall be considered when pre-assigning PDSCH resources.

Embodiment I d:

The present embodiment is the same as embodiments l a- l c in an aspect of reserved resource idea. Here, the reserved resources are relative to the user equipment, i. e. , some REs in the PDSCH resources allocated to each user equipment are fixedly reserved for confirmation of the PCFICH detection result. Contents saved in the reserved resources can be a pre-specified sequence with a certain length as the embodiment l a and the coding modulation manner of the contents can be the same as or different from that of the PDSCH that the contents belong to.

Procedures of the PDCCH cross-carrier indication mechanism in the LTE-A system adopting this method are illustrated in Fig. 9.

Steps 90 1 -905 are the same as steps 401 -405 and the step 907 is the same as step 406. Steps 906 and 908 different from Fig.4 are only described here .

Step 906: the user equipment extracts reserved resources from specified locations in the acquired PDSCH , obtains information included therein and compares it with the specified information. If they are the same, it means correct and the procedure will proceed to Step 907.

Step 908 : if the result of Step 906 is wrong, ACK/ NACK will not be fed back and the base station will detect the DTX later and performs corresponding processing.

Embodiment 2 :

As illustrated in Fig. 10, a PDCCH for a PDSCH on a carrier carrying the PDSCH resides on a carrier carrying the PDCCH . A mask relative to the number of control symbols on the carrier carrying the PDSCH is added into CRC (Cyclic Redundancy Check) , in DCI (Downlink Control Information) format, corresponding to the PDCCH . For example, in this method, firstly three 16-bit binary masks can be designed (see TS 16.212 V8.7.0, "Evolved Universal Terrestrial Radio Access (E-UTRA) ; Multiplexing and channel coding" in section 5.3.3.2 , a design method for user equipment transmit- antenna selection mask) . Then one of masks is selected according to the number of control information symbols on the carrier carrying the PDSCH and per-bit XOR (exclusive OR) is performed for the CRC in DCI format and the mask. Thus, the user equipment can implicitly acquire the control symbol number information (which originally can only be acquired from the PCFICH of the carrier carrying the PDSCH) on the carrier carrying the PDSCH by detecting different CRC masks when blindly detecting the PDCCH .

Procedures of the PDCCH cross-carrier indication mechanism in the LTE-A system adopting this method are illustrated in Fig. 1 1 .

Step 1 101 : the user equipment detects the PCFICH on the carrier carrying the PDCCH in the current sub-frame and acquires the number of control information symbols on the carrier in the sub-frame.

Step 1 102 : the PDCCH is blindly detected in the control region on the acquired carrier in the sub-frame according to RNTI and CRC mask.

Step 1 103 : If a correct PDCCH which is relative to downlink assignments and whose carrier indicator field is not null is detected, then the user equipment acquires resource block assignment information of the PDSCH , carrier indicator and HARQ information from the PDCCH , and acquires the control information symbol number information on the carrier carrying the PDSCH from the CRC mask corresponding to the PDCCH .

Step 1 104 : the user equipment extracts the PDSCH from the next OFDM symbol in the control region of the carrier in the current sub-frame according to the acquired resource block assignment information of the PDSCH and the acquired control information symbol number information on the carrier carrying the PDSCH . Step 1 105 : the user equipment places the PDSCH into an HARQ soft buffer according to the acquired HARQ information. Embodiment 3 :

In the present embodiment, considering that current 3GPP LTE-A standardization has decided to introduce a carrier indicator field with 1 -3 bits into the PDCCH cross- carrier indication structure, setting the carrier indicator field to fixedly be 3 bits will be able to reduce length categories of the DCI formats and mitigate the blind detection complexity. When the system bandwidth or a downlink bandwidth to which a user equipment is scheduled only includes two carriers or less, the carrier indicator field in the cross-carrier indication structure only needs 1 bit and the rest two redundancy two bits can be used to indicate three kinds of control information symbol number information on the carrier carrying the PDSCH . If the system bandwidth or a downlink bandwidth to which a user equipment is scheduled only includes more than two carriers, then this method needs to combine with other embodiments in the present invention or other methods not disclosed in the present invention to solve the problem to solved by the present invention.

Procedures of the PDCCH cross-carrier indication mechanism in the LTE-A system adopting this method are illustrated in Fig. 12.

Steps 120 1 - 1203 are the same as steps 40 1 -403 and the steps 1205- 1206 are the same as steps 405-406. Step 1204 different from Fig.4 is only described here.

Step 1204 : the user equipment extracts the control information symbol number information from the obtained carrier indicator and the procedure proceeds to Step 1205.

In the above embodiments, reserved resources, CRC mask, carrier indicator field and other necessary settings can be performed at the base station side. Although the operations of the base station are not described in details, the present invention mainly relates to cross-carrier indication processing at the user equipment side and those skills in the art would conceive any implementations required for the necessary settings on the basis of disclosures in the present invention.

Hardware implementation of the user equipment

Fig. 13 is a schematic drawing illustrating a user equipment structure configuration when considering solving the problem of HARQ buffer corruption caused by PCFICH errors. In order to clearly and briefly illustrate the technical solution of the present invention, the schematic diagram only shows key parts of the user equipment in the present invention and other general parts are omitted. In the following descriptions, descriptions on general parts are also omitted so as to avoid confusion in understanding.

According to the present invention, the user equipment can comprise a first carrier PCFICH detection unit configured to detect a PCFICH on the first carrier carrying a PDCCH and acquire the control information symbol number information on the first carrier; a PDCCH detection unit configured to detect the PDCCH on the first carrier and acquire PDSCH resource block assignment information, carrier indicator and HARQ information according to the control information symbol number information on the first carrier; a second carrier control information symbol number information detection unit configured to detect the control information symbol number information on the second carrier carrying a PDSCH, which is indicated by the acquired carrier indicator and a PDSCH acquisition unit configured to acquire or not acquire the PDSCH according to the control information symbol number information on the second carrier and/ or PDSCH resource block assignment information. The user equipment can further comprise a PDSCH buffer unit configured to place PDSCH obtained by the PDSCH acquisition unit into an HARQ soft buffer according to the acquired HARQ information.

In details, the second carrier control information symbol number information detection unit of the user equipment can conduct processing as that in Embodiment l a or l c. Here, as shown in Fig. 14a, the second carrier control information symbol number information detection unit can comprise a second carrier PCFICH detection unit configured to detect PCFICH on the second carrier and acquire the control information symbol number information indicated by the PCFICH as a PCFICH detection result, a reserved resource detection unit configured to determine locations of reserved resources and acquire the reserved resources from the determined locations according to the PCFICH detection result, and a comparison unit configured to compare contents in the reserved resources with pre- specified contents. The PDSCH acquisition unit acquires the PDSCH according to the control information symbol number information indicated by the PCFICH and the PDSCH resource block assignment information when contents compared by the comparison unit are the same. If the contents are different, the PDSCH acquisition unit will not acquire the PDSCH . Thus the user equipment can obtain confirmation on the PCFICH detection result of the carrier carrying the PDSCH and can detect and avoid error detection.

Alternatively, the second carrier control information symbol number information detection unit of the user equipment can conduct processing as that in Embodiment l b or I d . Here, as shown in Fig. 14b, the second carrier control information symbol number information detection unit can comprise a joint detection unit configured to jointly detect the PCFICH on the second carrier and the reserved resources obtained from pre-specified locations and a decision unit configured to determine the control information symbol number information on the second carrier according to the joint detection results. Here , the PDSCH acquisition unit acquires the PDSCH according to the control information symbol number information on the second carrier determined by the decision unit and the PDSCH resource block assignment information . Thus, the user equipment can directly join the detection procedure for the PCFICH on the carrier carrying the PDSCH and the detection accuracy can be improved.

Alternatively, the second carrier control information symbol number information detection unit can conduct processing as that in Embodiment 2 , i. e. , detecting a CRC mask corresponding to the PDCCH carried by the first carrier and acquiring the control information symbol number information on the second carrier. Optionally, the second carrier control information symbol number information detection unit can conduct processing as that in Embodiment 3, i. e. , extracting the control information symbol number information on the carrier carrying the PDSCH from two redundancy bits in the carrier indicator field when the number of the system bandwidths is less than or equal to two carriers. Here, the PDSCH acquisition unit acquires the PDSCH according to the acquired control information symbol number information on the second carrier and the PDSCH resource block assignment information . Thus, the user equipment can directly acquire the control information symbol number information from the CRC mask or the carrier indicator instead of from the PCFICH detection, and avoid possible errors that are resulted from the PCFICH detection. It is to be noted that in the above descriptions the technical solution of the present invention is explained in a way of schematic examples, however the present invention is not limited to the above steps and units. In some circumstances, the steps and units may be adjusted and accepted or rejected based on the demands. Therefore, some steps and units are not necessary for implementing the invention idea of the present invention. Therefore, the necessary technical features of the present invention are only restricted by the lowest requirements for implementing the invention idea of the present invention and are not restricted by the above detailed embodiments.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the systems, methods, and apparatus described herein without departing from the scope of the claims.

Claims

1. A cross-carrier indication method, comprising:

detecting a PCFICH (physical format indication channel) on a first carrier carrying a PDCCH (physical downlink control channel) and acquiring control information symbol number information on the first carrier,

detecting the PDCCH on the first carrier and acquiring PDSCH (physical downlink share channel) resource block assignment information, a carrier indicator and HARQ (hybrid automatic request) information according to the control information symbol number information on the first carrier, detecting control information symbol number information on a second carrier carrying a PDSCH , which is indicated by the acquired carrier indicator, and

acquiring or not acquiring the PDSCH according to the acquired control information symbol number information on the second carrier and/ or the PDSCH resource block assignment information.

2. The method of claim 1 , wherein the step of detecting the control information symbol number information on the second carrier comprises detecting a carrier indicator field in the acquired carrier indicator and acquiring the control information symbol number information on the second carrier.

3. The method of claim 2 , wherein a length of the carrier indicator field is fixed to be three bits, and

two redundancy bits in the carrier indicator field are used to indicate the control information symbol number information on the second carrier when a system bandwidth covers less than or equal to two carriers.

4. The method of claim 1 , wherein the step of detecting the control information symbol number information on the second carrier comprises detecting a CRC (cyclic redundancy check) mask corresponding to the PDCCH carried by the first carrier and acquiring the control information symbol number information on the second carrier, wherein

the CRC mask is obtained by adding a mask relative to the control information symbol number information on the second carrier to a CRC, in DCI (downlink control information) format, corresponding to the PDCCH carried by the first carrier.

5. The method of any one of claim 2 through claim 4 , wherein the step of acquiring or not acquiring the PDSCH comprises acquiring the PDSCH according to the acquired control information symbol number information on the second carrier and the PDSCH resource block assignment information.

6. The method of claim 5 , further comprising:

placing the acquired PDSCH into an HARQ soft buffer according to the acquired HARQ information.

7. The method of claim 1 , wherein the step of detecting the control information symbol number information on the second carrier comprises:

detecting the PCFICH on the second carrier and acquiring the control information symbol number information indicated by the PCFICH as a PCFICH detection result,

determining a location of a reserved resource and acquiring the reserved resource from the determined location according to the PCFICH detection result, and

comparing contents in the reserved resource with pre- specified contents, wherein

the location of the reserved resource is relative to the control information symbol number information on the second carrier and the contents of the reserved resource are pre- specified between a base station and a user equipment.

8. The method of claim 7 , wherein the step of acquiring or not acquiring the PDSCH comprises:

acquiring the PDSCH according to the control information symbol number information indicated by the PCFICH and the PDSCH resource block assignment information, if the contents are the same, and

not acquiring the PDSCH , if the contents are different.

9. The method of claim 8, further comprising:

after acquiring the PDSCH , placing the acquired PDSCH into an HARQ soft buffer according to the acquired HARQ information.

10. The method of claim 1 , the step of detecting the control information symbol number information on the second carrier comprises :

jointly detecting the PCFICH on the second carrier and a reserved resource extracted from a pre-specified location, and determining the control information symbol number information on the second carrier according to the joint detection result, wherein

the location of the reserved resource is relative to the control information symbol number information on the second carrier and the location of the reserved resource is pre- specified between a base station and a user equipment.

1 1 . The method of claim 10, wherein contents of the reserved resource are obtained by coding the control information symbol number information on the second carrier.

12. The method of claim 10 , wherein the step of acquiring or not acquiring PDSCH comprises acquiring the PDSCH according to the determined control information symbol number information on the second carrier and the PDSCH resource block assignment information.

13. The method of claim 12 , further comprising:

14. The method of claim 7 or claim 10 , wherein the reserved resource is a resource reserved in a control region or a data region of the second carrier.

15. The method of claim 14, wherein the reserved resource is resource elements or control channel elements in the control region of the second carrier, or

the reserved resource is resource elements in the data region of the second carrier or resource elements in the PDSCH allocated by the user equipment.

16. The method of claim 15 , wherein a temporal location of the reserved resource is the fourth OFDM (orthogonal frequency division multiplexing) symbol in a sub- frame and a frequency density is that each resource block has one resource element.

17. A user equipment capable of cross-carrier indication, comprising:

a first carrier PCFICH (physical format indication channel) detection unit configured to detect a PCFICH on a first carrier carrying a PDCCH (physical downlink control channel) and acquiring control information symbol number information on the first carrier,

a PDCCH detection unit configured to detect the PDCCH on the first carrier and acquire PDSCH (physical downlink share channel) resource block assignment information, a carrier indicator and HARQ (hybrid automatic request) information according to the control information symbol number information on the first carrier,

a second carrier control information symbol number information detection unit configured to detect control information symbol number information on a second carrier carrying a PDSCH indicated by the acquired carrier indicator, and

a PDSCH acquisition unit configured to acquire or not acquire PDSCH according to the acquired control information symbol number information on the second carrier and/ or the PDSCH resource block assignment information.

18. The user equipment of claim 17 , wherein the second carrier control information symbol number information detection unit detects a carrier indicator field in the acquired carrier indicator and acquires the control information symbol number information on the second carrier.

19. The user equipment of claim 17, wherein the second carrier control information symbol number information detection unit detects a CRC (cyclic redundancy check) mask corresponding to the PDCCH carried by the first carrier and acquires the control information symbol number information on the second carrier, wherein

20. The user equipment of claim 18 or claim 19 , wherein the PDSCH acquisition unit acquires the PDSCH according to the acquired control information symbol number information on the second carrier and the PDSCH resource block assignment information.

2 1 . The user equipment of claim 20, further comprising a PDSCH buffer unit configured to place the acquired PDSCH into an HARQ soft buffer according to the acquired HARQ information.

22. The user equipment of claim 17, wherein the second carrier control information symbol number information detection unit comprises:

a second carrier PCFICH detection unit configured to detect the PCFICH on the second carrier and acquire the control information symbol number information indicated by the PCFICH as a PCFICH detection result,

a reserved resource detection unit configured to determine a location of a reserved resource and acquire the reserved resource from the determined location according to the PCFICH detection result, and

a comparison unit configured to compare contents in the reserved resource with pre-specified contents, wherein

the location of the reserved resource is relative to the control information symbol number information on the second carrier and the contents of the reserved resource are pre- specified between a base station and the user equipment.

23. The user equipment of claim 22 , wherein the PDSCH acquisition unit acquires the PDSCH according to the control information symbol number information indicated by the PCFICH if the contents compared by the comparison unit are the same, and does not acquire the PDSCH if the contents are different.

24. The user equipment of claim 23, further comprising a PDSCH buffer unit configured to place the PDSCH acquired by the PDSCH acquisition unit into an HARQ soft buffer according to the acquired HARQ information.

25. The user equipment of claim 17, wherein the second carrier control information symbol number information detection unit comprises:

a joint detection unit configured to jointly detect the

PCFICH on the second carrier and a reserved resource extracted from a pre-specified location, and

a decision unit configured to determine the control information symbol number information on the second carrier according to the j oint detection result, wherein

the location of the reserved resource is relative to the control information symbol number information on the second carrier and the location of the reserved resource is pre- specified between a base station and the user equipment.

26. The user equipment of claim 25 , wherein the PDSCH acquisition unit acquires the PDSCH according to the control information symbol number information determined by the decision unit and the PDSCH resource block assignment information.

27. The user equipment of claim 26, further comprising a PDSCH buffer unit configured to place the PDSCH acquired by the PDSCH acquisition unit into an HARQ soft buffer according to the acquired HARQ information.