WO2015061947A1

WO2015061947A1 - Method and apparatus for obtaining dci of the interfering cell based on common pdcch/epdcch sets

Info

Publication number: WO2015061947A1
Application number: PCT/CN2013/086078
Authority: WO
Inventors: Shin Horng Wong; Matthew Baker; Qi JIANG; Fang-Chen Cheng; Sigen Ye
Original assignee: Alcatel Lucent; Alcatel-Lucent Shanghai Bell Co., Ltd.
Priority date: 2013-10-28
Filing date: 2013-10-28
Publication date: 2015-05-07
Also published as: TW201528711A; TWI552538B

Abstract

The invention provides a method for use in an interfering cell which includes one or more interfering user equipments interfering a victim user equipment of a victim cell, wherein the method comprises the steps of: configuring one or more common PDCCH/EPDCCH sets; informing the victim cell of information about the one or more common PDCCH/EPDCCH sets; and broadcasting network assistance information, the network assistance information including ID of each of interfering user equipment, wherein for each interfering user equipment, an PDCCH/EPDCCH candidate is selected from the EPDCCH set of the interfering user equipment to carry downlink control information of the interfering user equipment and the selected PDCCH/EPDCCH candidate is also contained in the one or more common PDCCH/EPDCCH sets. The invention also provides a method for use in a victim user equipment of a victim cell, the victim user equipment suffering interferences from one or more interfering user equipments of an interfering cell, wherein the method comprises the steps of: receiving information about one or more common PDCCH/EPDCCH sets from the victim cell; receiving network assistance information from the interfering cell, the network assistance information including ID of each interfering user equipment; and decoding the one or more common PDCCH/EPDCCH sets using the ID of each interfering user equipment to obtain downlink control information of each interfering user equipment.

Description

METHOD AND APPARATUS FOR OBTAINING PCI OF THE INTERFERING CELL BASED ON COMMON PDCCH/EPDCCH SETS

Field of the Invention

The application relates to communication systems.

Background of the Invention

A Study Item on Network Assisted Interference Suppression & Cancellation (NAISC) has been agreed for Release 12 in 3GPP for LTE. NAISC is useful in heterogeneous network (HetNet) especially for the user equipment (UE) in the Cell Range Expansion

(CRE) region as shown in figure 1 where the UE experiences strong interference from the macro cell. In NAISC, the network would provide downlink decoding information of at least one UE from an interfering neighbor cell to the UEs in a victim cell. For example in figure 1, the downlink decoding information for one or more UEs in the macro cell (i.e. the interfering cell) is signaled to the UE in the CRE region of the small cell (i.e. the victim cell). The UE in the CRE region can therefore decode the transmission for these UEs in the macro cell and remove their signal (i.e. interference) from its received signal. This downlink decoding information of the interfering cell, referred to as network assistance information, can be signaled to more than one UE in the victim cell. It should be appreciated that NAISC can also be used in homogenous network.

Since scheduling information from the interfering cell is required, coordination between interfering and victim cells may be required. Due to the delay in the backhaul (e.g. X2) the interfering cell need to schedule in advance such that the network assistance information is still valid when it reaches the victim cell (and the victim UE). Coordination and sharing of scheduling information between cells would add complexity to the eNB. Recognizing this, it was proposed that the interfering cell broadcasts the network assistance information. Since the interfering cell is aware of its own scheduling, this proposal avoids the need to signal the network assistance information to the victim cell and avoids the need for the interfering cell to schedule in advance. Furthermore the network assistance information will only reach UEs that are affected by interference.

The scheme where the interfering cell broadcasts the network assistance information was proposed in UMTS for NAISC in HetNet. It is further proposed in UMTS that only the UE ID of the interfering UE is required in the network assistance information. The victim UE would use the interfering UE ID to decode the HS-SCCH (downlink control channel) and thereby obtains the decoding information for the interfering data channel (i.e. HS-PDSCH). These two methods have received favorable support in UMTS since it avoids coordination between cells. Given the advantages, it is therefore attractive to also apply these schemes in LTE. However, unlike in UMTS, the downlink control channel, i.e. the EPDCCHs and PDCCHs in LTE are blindly decoded. Since the set of PDCCH/EPDCCH candidates are UE specific, coordination between cells are required to signal the PDCCH/EPDCCH candidates for the interfering UE. Although full scheduling need not be made in advance for the interfering cell, the interfering cell would still need to at least determine which UE to schedule for in advance in order to share the PDCCH/EPDCCH candidates with the victim cell. The technical problem to solve is therefore to avoid having to share any scheduling information and thereby avoids any dynamic coordination between the interfering and victim cells.

Object and Summary of the Invention

Based on above concerns, the main idea of this invention is to introduce one or more common PDCCH/EPDCCH sets that are known to both the interfering cell and victim cell. The common PDCCH/EPDCCH sets are signaled to the UE when it is configured to receive network assistance information (broadcasted by the interfering cell). If an interfering UE is scheduled and its ID is indicated in the network assistance information, the PDCCH/EPDCCH candidate used for this interfering UE is selected from the one or more common PDCCH/EPDCCH sets. Therefore the one or more common PDCCH/EPDCCH sets should be chosen such that they overlap with the configured search spaces of any UEs that might be indicated in the network assistance information.

In one aspect of the invention, there is provided a method for use in an interfering cell which includes one or more interfering user equipments interfering a victim user equipment of a victim cell, wherein the method comprises the steps of:

- configuring one or more common PDCCH/EPDCCH sets;

- informing the victim cell of information about the one or more common

PDCCH/EPDCCH sets;

- broadcasting network assistance information, the network assistance information including ID of each of interfering user equipment;

wherein for each interfering user equipment, an PDCCH/EPDCCH candidate is selected from the PDCCH/EPDCCH set of the interfering user equipment to carry downlink control information of the interfering user equipment and the selected PDCCH/EPDCCH candidate is also contained in the one or more common

PDCCH/EPDCCH sets.

Advantageously, the method further comprises the steps of:

- sending downlink control information of the interfering user equipment on the selected PDCCH/EPDCCH candidate.

Accordingly, in another aspect of the invention, there is provided a method for use in a victim user equipment of a victim cell, the victim user equipment suffering interferences from one or more interfering user equipments of an interfering cell, wherein the method comprises the steps of:

- receiving information about one or more common PDCCH/EPDCCH sets from the victim cell;

- receiving network assistance information from the interfering cell, the network assistance information including ID of each interfering user equipment;

- decoding the one or more common PDCCH/EPDCCH sets using the ID of each interfering user equipment to obtain downlink control information of each interfering user equipment.

With the foresaid solution of the invention, there is no need to use dynamic signaling between the interfering and victim cells. The coordination required here is only the semi-static details of the common PDCCH/EPDCCH sets. The interfering cell need only inform the victim cell of the common PDCCH/EPDCCH sets only once or whenever the interfering cell reconfigures the candidates in the common PDCCH/EPDCCH sets, which is expected to be infrequent.

Moreover, for one interfering UE, as the victim UE only needs to decode the common PDCCH/EPDCCH sets, the number of PDCCH/EPDCCH candidates that the victim UE would have to search for the downlink control information of the interfering UE would be reduced.

It should be appreciated that the common PDCCH/EPDCCH sets of an interfering cell can be shared with more than one victim cell. Similarly a victim cell can have common PDCCH/EPDCCH sets belong to different interfering cells. These common PDCCH/EPDCCH sets may or may not overlap.

In one embodiment, the network assistance information further includes, for each interfering user equipment, a set-index for indicating which set of the one or more common PDCCH/EPDCCH sets the interfering user equipment corresponds to, wherein the step of decoding comprises:

- decoding the common PDCCH/EPDCCH set indicated by the set-index using the ID of the interfering user equipment to obtain downlink control information of the interfering user equipment.

For one interfering UE, the victim UE only needs to decode the common PDCCH/EPDCCH set indicated by the set-index, which further reduces the number candidates that the victim UE has to search for the interfering UE's downlink control information.

It should be appreciated that one index can be associated with more than one interfering UE and that such an association is dynamic and can change from one subframe to another.

In another embodiment, the network assistance information further includes, for each interfering user equipment, a subset-index for indicating which subset of the common PDCCH/EPDCCH set the interfering user equipment corresponds to, wherein the step of decoding comprises:

- decoding the subset of the common PDCCH/EPDCCH set indicated by the subset-index using the ID of the interfering user equipment to obtain downlink control information of the interfering user equipment.

For one interfering UE, the victim UE only needs to decode the subset of the common PDCCH/EPDCCH set indicated by the subset-index, which further reduces the number candidates that the victim UE has to search for the interfering UE's downlink control information. In one example, the subset contains only one PDCCH/EPDCCH candidate and therefore the network assistance information indicates the exact candidate.

The ID of the interfering UE included in the network assistance information can be the interfering UE's C-RNTI, for example.

In another embodiment, a set of potential interfering C-RNTIs can be signaled to the victim UE during configuration of this common PDCCH/EPDCCH set. The victim UE would try to decode the common PDCCH/EPDCCH sets using these signaled C-RNTIs. This would reduce the amount of dynamic signaling required of the interfering cell. In a further embodiment, the interfering cell would only broadcast an interfering UE's C-RNTI if it differs from those in the said set of potential interfering C-RNTI.

For example, the number of PDCCH/EPDCCH candidates in a common PDCCH/EPDCCH set is equal to the number of additional candidates required for SU-MIMO. The number of PDCCH/EPDCCH candidates for single stream is 32 and that for SU-MIMO is 44. The common PDCCH/EPDCCH set would therefore contain 12 candidates per C-RNTI. This would maintain the flexibility for the victim UE in scheduling for its PDCCH/EPDCCH whilst not increasing the blind decodes beyond that of a SU-MIMO capable UE. It should be noted that NAISC can also be used for MU-MIMO, and since it is difficult for a UE to operate in SU-MIMO and also MU-MIMO mode at the same subframe, we can use the candidates for SU-MIMO for the interfering UE in MU-MIMO.

In another embodiment, a common PDCCH/EPDCCH set contains one or more candidates in the common search space on PDCCH, or EPDCCH if common search space is defined on EPDCCH in the future. This allows the eNB to schedule any interfering UE using one of the candidates in the common search space

Brief Description of the Drawings

The invention is explained in further detail, and by way of example, with reference to the accompanying drawings wherein:

Figure 1 shows a topology of a HetNet network;

Figure 2 shows a flow chart of a method for use in an interfering cell of a communication system according to one embodiment of the invention;

Figure 3 shows one example of the common PDCCH/EPDCCH sets.

Throughout the above drawings, like reference numerals will be understood to refer to like, similar or corresponding features or functions.

Detailed Description

Illustrative embodiments are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions should be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The disclosed subject matter will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the description with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the disclosed subject matter. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.

Hereinafter, one embodiment of the invention will be described referring to figure 2 and in conjunction with figure 1.

Assume the HetNet scenario in figure 1 where the macro cell is the interfering cell and the victim UE is in the CRE region of a small cell (i.e. the victim cell). Both the macro cell and the small cell have a system bandwidth of 20 PRBs.

First, in step S201, the interfering cell (i.e. the macro cell) configures two common

PDCCH/EPDCCH sets, as shown in figure 3, where:

1) Common EPDCCH Set 1 contains PRB3, PRB6, PRB9, PRB12, PRB15 and PRB18.

2) Common EPDCCH Set 2 contains PRB2, PRBS, PRB10, PRB14, PRB16 and PRB20.

Then, in step S202, the interfering cell informs the victim cell of information about the configured two PDCCH/EPDCCH sets, and also broadcasts network assistance information in which IDs of one or more interfering cells are included. The victim cell then signals the information to the victim UE when it is configured to operate with NAISC.

Consider an interfering UE with an EPDCCH set containing PRB2, PRB6, PRB10, PRB12, PRB16 and PRB19. It can be observed that the PRBs for this interfering cell overlaps with some of the PRBs in Common EPDCCH Set 1 and Common EPDCCH Set 2. The number of ECCEs in Common EPDCCH Set 1 and Common EPDCCH Set 2 are the same and for simplicity they all have the same number of EPDCCH candidates in each aggregation level). Also it is assumed that an EPDCCH candidate spans only 1 PRB.

To be specific, at subframe n, the interfering cell broadcasts the interfering UE ID (e.g., C-RNTI) in the network assistance information. The interfering cell decides to use an EPDCCH candidate in PRB 10 to carry the DCI message. Since Common EPDCCH Set 2 also contains the same candidate in PRB 10, index 2 (referring to Common EPDCCH Set 2) is also transmitted and associated with this interfering UE ID. The victim UE receives the index to Common EPDCCH Set 2 and together with the interfering UE ID, and it can decode the Common EPDCCH Set 2 indicated by the index using the interfering UE ID to obtain the downlink control information of the interfering UE. The downlink control information contains scheduling information for the interfering PDSCH, and the victim UE can then use this information to cancel the interference from the interfering UE.

It should be noted that the above described embodiments are given for describing rather than limiting the invention, and it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art readily understand. Such modifications and variations are considered to be within the scope of the invention and the appended claims. The protection scope of the invention is defined by the accompanying claims. In addition, any of the reference numerals in the claims should not be interpreted as a limitation to the claims. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The indefinite article "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps.

Claims

What is claimed is:

1. A method for use in an interfering cell which includes one or more interfering user equipments interfering a victim user equipment of a victim cell, wherein the method comprises the steps of:

- configuring one or more common PDCCH/EPDCCH sets;

informing the victim cell of information about the one or more common PDCCH/EPDCCH sets;

wherein for each interfering user equipment, an PDCCH/EPDCCH candidate is selected from the PDCCH/EPDCCH set of the interfering user equipment to carry downlink control information of the interfering user equipment and the selected PDCCH/EPDCCH candidate is also contained in the one or more common PDCCH/EPDCCH sets.

2. The method of claim 1, wherein the method further comprises the step of:

3. The method of claim 2, wherein the network assistance information further includes, for each interfering user equipment, a set-index for indicating which set of the one or more common PDCCH/EPDCCH sets the interfering user equipment corresponds to.

4. The method of claim 3, wherein the network assistance information further includes, for each interfering user equipment, a subset-index for indicating which subset of the common PDCCH/EPDCCH set the interfering user equipment corresponds to.

5. The method of claim 1, wherein the ID of each of interfering user equipment is C-RNTI.

6. A method for use in a victim user equipment of a victim cell, the victim user equipment suffering interferences from one or more interfering user equipments of an interfering cell, wherein the method comprises the steps of:

- decoding the one or more common PDCCH/EPDCCH sets using the ID of each interfering user equipment respectively to obtain downlink control information of each interfering user equipment.

7. The method of claim 6, wherein the network assistance information further includes, for each interfering user equipment, a set-index for indicating which set of the one or more common PDCCH/EPDCCH sets the interfering user equipment corresponds to, wherein the step of decoding comprises:

8. The method of claim 7, wherein the network assistance information further includes, for each interfering user equipment, a subset-index for indicating which subset of the common PDCCH/EPDCCH set the interfering user equipment corresponds to, wherein the step of decoding comprises:

9. An apparatus for use in an interfering cell which includes one or more interfering user equipments interfering a victim user equipment of a victim cell, wherein the apparatus comprises:

a configuring unit for configuring one or more common PDCCH/EPDCCH sets;

an informing unit for informing the victim cell of information about the one or more common PDCCH/EPDCCH sets;

a broadcasting unit for broadcasting network assistance information, the network assistance information including ID of each of interfering user equipment; wherein for each interfering user equipment, an PDCCH/EPDCCH candidate is selected from the EPDCCH set of the interfering user equipment to carry downlink control information of the interfering user equipment and the selected PDCCH/EPDCCH candidate is also contained in the one or more common PDCCH/EPDCCH sets.

10. The apparatus of claim 9, wherein the apparatus further comprises:

a sending unit for sending downlink control information of the interfering user equipment on the selected PDCCH/EPDCCH candidate.

11. The apparatus of claim 10, wherein the network assistance information further includes, for each interfering user equipment, a set-index for indicating which set of the one or more common PDCCH/EPDCCH sets the interfering user equipment corresponds to.

12. The apparatus of claim 1, wherein the network assistance information further includes, for each interfering user equipment, a subset-index for indicating which subset of the common PDCCH/EPDCCH set the interfering user equipment corresponds to.

13. An apparatus for use in a victim user equipment of a victim cell, the victim user equipment suffering interferences from one or more interfering user equipments of an interfering cell, wherein the apparatus comprises:

a first receiving unit for receiving information about one or more common PDCCH/EPDCCH sets from the victim cell;

a second receiving unit for receiving network assistance information from the interfering cell, the network assistance information including ID of each interfering user equipment;

a decoding unit for decoding the one or more common PDCCH/EPDCCH sets using the ID of each interfering user equipment respectively to obtain downlink control information of each interfering user equipment.

14. The apparatus of claim 13, wherein the network assistance information further includes, for each interfering user equipment, a set-index for indicating which set of the one or more common PDCCH/EPDCCH sets the interfering user equipment corresponds to, wherein the decoding unit is further for decoding the common PDCCH/EPDCCH set indicated by the set-index using the ID of the interfering user equipment to obtain downlink control information of the interfering user equipment.

15. The apparatus of claim 14, wherein the network assistance information further includes, for each interfering user equipment, a subset-index for indicating which subset of the common PDCCH/EPDCCH set the interfering user equipment corresponds to, wherein the decoding unit is further for decoding the subset of the common PDCCH/EPDCCH set indicated by the subset-index using the ID of the interfering user equipment to obtain downlink control information of the interfering user equipment.