WO2012124715A1

WO2012124715A1 - Communication methods and base stations using the same

Info

Publication number: WO2012124715A1
Application number: PCT/JP2012/056489
Authority: WO
Inventors: Ming Ding; Zeng YANG; Lei Huang; Renmao Liu
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2011-03-11
Filing date: 2012-03-07
Publication date: 2012-09-20
Also published as: CN102685864A; CN102685864B

Abstract

A communication method and a base station using the same are disclosed. The communication method comprises the following steps: a first base station receives data muting information from a second base station via backhaul communication, wherein said data muting information contains an identity (ID) of the first base station and a positional indication for data muting; and the first base station performs data muting at positions indicated by said positional indication for data muting.

Description

DESCRIPTION

TITLE OF INVENTION :

COMMUNICATION METHODS AND BASE STATIONS

USING THE SAME TECHNICAL FIELD

The invention relates to communication technology, and more particularly, to communication methods and base stations (BSs) using the same. BACKGROUND ART

Multi-antenna wireless transmission technique, or Multiple In Multiple Out (MIMO) , can achieve spatial multiplex gain and spatial diversity gain by deploying a plurality of antennas at both the transmitter and the receiver and utilizing the spatial resources in wireless transmission. Researches on information theory have shown that the capacity of a MIMO system grows linearly with the minimum of the number of transmitting antennas and the number of receiving antennas. Fig. 1 shows a schematic diagram of a MIMO system . As shown in Fig. 1 , a plurality of antennas at the transmitter and a plurality of antennas at each of the receivers constitute a multi-antenna wireless channel containing spatial domain information . Further, Orthogonal Frequency Division Multiplexing (OFDM) technique has a strong anti-fading capability and high frequency utilization and is thus suitable for high speed data transmission in a multi-path and fading environment. The MIMO-OFDM technique, in which MIMO and OFDM are combined, has become a core technique for a new generation of mobile communication.

For instance, the 3^rd Generation Partnership Project (3GPP) organization is an international organization in mobile communication field and plays an important role in standardization of 3G cellular communication technologies . Since the second half of the year 2004 , the 3GPP organization has initiated a so-called Long Term Evolution (LTE) project for designing Evolved Universal Terrestrial Radio Access (EUTRA) and Evolved Universal Terrestrial Radio Access Network (EUTRAN) . The MIMO-OFDM technique is employed in the downlink of the LTE system. In a conference held in Shenzhen, China in April 2008 , the 3GPP organization started a discussion on the standardization of 4G cellular communication systems (currently referred to as LTE-A systems) . In this conference, a concept known as "multi-antenna multi-BS coordination" gets extensive attention and support. Its core idea is that multiple BSs can provide communication services for one or more user equipments (UEs) simultaneously, so as to improve data transmission rate for a UE located at the edge of a cell.

With regard to the multi-antenna multi-BS coordination, fundamental agreements are mainly available from the following standard document by March, 2010 : 3GPP TR 36.8 14 V9.0.0 (20 10-03) , "Further advancements for E-UTRA physical layer aspects (Release 9)" , which can be outlined as follows:

· In a multi-antenna multi-BS service, a UE needs to report channel state / statistical information of a link between the UE and each BS / cell in a set of cells. This set of cells is referred to as a measurement set for multi-antenna multi-BS transmission .

· The set of BSs / cells for which the UE actually performs information feedback can be a subset of the measurement set and is referred to as a coordination set for multi-antenna multi-BS transmission. Here , the coordination set for multi-antenna multi-BS transmission can be the same as the measurement set for multi-antenna multi-BS transmission.

• A BS / cell in the coordination set for multi-antenna multi-BS transmission participates in Physical Downlink Shared Channel (PDSCH) transmission for the UE, either directly or indirectly.

• The scheme in which multiple BSs directly participate in coordination transmission is referred to as Joint Processing (JP) . The JP scheme needs to share PDSCH signal of the UE among the multiple BSs participating the coordination and can be divided into two approaches . One is referred to as Joint Transmission (JT) in which the multiples BSs transmit their PDSCH signals to the UE simultaneously. The other one is referred to as Dynamic Cell Selection (DCS) in which at any time instance, only one of the BSs which has the strongest signal link is selected to transmit its PDSCH signal to the UE.

• The scheme in which multiple BSs indirectly participate in coordination transmission is referred to as Coordinated Beamforming/ Coordinated Scheduling (CB / CS) . In this CB / CS scheme, instead of sharing PDSCH signal of the UE among the multiple BSs participating in the coordination, the beams / resources for transmission of PDSCHs for different UEs are coordinated among the multiple BSs to suppress the interference between each other.

• For a UE operating in the multi-antenna multi-BS coordinated transmission environment, information feedback is mainly carried out separately for each BS and is transmitted over the uplink resources of the serving BS .

With regard to JP, a UE often needs a larger amount of channel state information, in order to achieve better system performance . Therefore, it is desirable for multiple BSs to transmit high-quality channel state information - downlink reference signals, which are used by the UE to detect channel state . For improving the quality of channel state information - downlink reference signals, a data muting scheme (i . e . PUSCH muting) is proposed for LTE-A systems. In this scheme, a BS mutes its data transmission where other BSs' channel state information - downlink reference signals occur, so that other BSs' channel state information - downlink reference signals will be interfered less heavily (see non-patent document: 3GPP TSG RAN WG 1 , R l - 106522 , Huawei, HiSilicon, NTT Docomo, Samsung, LG Electronic , CATT, Panasonic, "Way forward on CSI-RS and muting configurations exchange over X2 interface" .

With regard to CB / CS, in LTE systems, there is a method for controlling downlink transmission power on per spectral resource block basis, wherein a BS transmits a transmission power indication to neighboring BSs on per spectral resource block basis, indicating for each spectral resource block whether the transmission power of the BS exceeds a preset threshold. Upon reception of the transmission power indication, neighboring BSs may take resource scheduling measures or the like , so as not to assign a UE to a spectral resource block suffering from heavy interference (see 3GPP TS 36.423, "X2 application protocol") . Such a method for controlling downlink transmission power has many advantages, such as simplicity, flexibility, and low signaling overhead.

Further, in 3GPP TR 36.8 14 V9.0.0, "Evolved Universal Terrestrial Radio Access (E-UTRA) ; Further advancements for E-UTRA physical layer aspects, 3GPP", several concepts and basic terms are defined for multi-antenna multi-BS coordinated scenarios, wherein : Serving cell, as already defined in LTE, refers to a single cell over which a Physical Downlink Control Channel (PDCCH) is transmitted.

In a multi-antenna multi-BS service, a UE needs to report channel state / statistical information of a link between the UE and a BS in each of a set of cells . This set of cells is referred to as a multi-antenna multi-BS coordination measurement set. This set of cells for which the UE actually performs information feedback can be a subset of the measurement set and is referred to as reported cells. Here , the measurement set can be the same as a cooperating set for multi-antenna multi-BS coordination, in which the BS in each of the cells participates in Physical Downlink Shared Channel (PDSCH) transmission for the UE, either directly or indirectly. The cooperating set may or may not be transparent to the UE. For a UE configured to operate in the multi-antenna multi-BS coordination mode, information feedback is mainly carried out separately for each BS and is transmitted over the uplink resources of the serving BS .

In the 50^th 3GPP RAN conference, research subj ects related to^'multi-antenna multi-BS coordination are adjusted for LTE Rel- 1 1 (see RP- 101425 , "Revised SID Proposal: Coordinated Multi-point Operation for LTE" , Samsung) . In order to enlarge its application scope, unconventional deployment scenarios, such as heterogeneous networks and or intra-cell distributed Remote Radio Unit, are included in the research scope of multi-antenna multi-BS coordination . According to the 63^rd bis 3GPP RAN I conference, research on multi-antenna multi-BS coordination will be directed at the following four deployment scenarios:

Scenario 1 : intra-BS multi-antenna multi-BS coordination;

Scenario 2 : inter-BSs multi-antenna multi-BS coordination;

Scenario 3 (multiple cell-IDs) : all transmission points in the range of a macrocell have different cell-IDs ;

Scenario 4 (shared cell-ID) : all transmission points in the range of a macrocell have the same cell-ID .

In the above scenarios, it is commonly assumed that communication links between transmission points have low delay and unlimited capacity. This is also a direct benefit from the deployment of distributed Remote Radio Units (RRUs) . As optical fiber is generally used as the medium connecting transmission points, restrictions on transmission delay and bandwidth are less stern . In the above multi-antenna multi-BS — -coordination scenarios, no matter whether transmission points share the same cell-ID , it is necessary for each transmission point to have a separate Channel State Information - Reference Signal (CSI-RS) pattern, so that effective Channel State Information (CSI) feedback can be achieved for the transmission point. In current standards, there is lack of discussion about backhaul communication between BSs associated with data muting and/ or downlink transmission power control in the above multi-antenna multi-BS coordinated scenario 4. The present invention is mainly made to fill this blank.

SUMMARY OF INVENTION

It is an object of the present invention to enable data muting and downlink transmission power control in the multi-antenna multi-BS coordinated scenario 4 .

In order to enable data muting in the multi-antenna multi-B S coordinated scenario 4 , according to the first aspect of the present invention, there is provided a communication method and a base station using the same . The communication method comprises the following steps: a first base station receives data muting information from a second base station via backhaul communication, wherein said data muting information contains an identity (ID) of the first base station and a positional indication for data muting; and the first base - station performs data muting at positions indicated by said positional indication for data muting.

According to the second aspect of the present invention, there is provided another communication method and a base station using the same . The communication method comprises the following steps: a second base station generates data muting information, which contains an ID of a first base station and a positional indication for data muting; and the second base station transmits said data muting information to said first base station via backhaul communication .

In order to enable downlink transmission power control in the multi-antenna multi-BS coordinated scenario 4 , according to the third aspect of the present invention, there is provided a communication method and a base station using the same . The communication method comprises the following steps: a first base station receives downlink transmission power control information from a second base station via backhaul communication, wherein said downlink transmission power control information contains an ID of the first base station and a transmission power indication, said transmission power indication indicating whether a transmission power exceeds a transmission power threshold and being generated on per spectral resource block basis ; and the first base station performs resource scheduling so as to prevent a user equipment from being assigned to a spectral resource block for which said transmission power indication indicates that the transmission power threshold is exceeded .

According to the fourth aspect of the present invention, there is provided another communication method and a base station using the same . The communication method comprises the following steps: a second base station generates downlink transmission power control information, which contains an ID of the first base station and a transmission power indication , said transmission power indication indicating whether a transmission power exceeds a transmission power threshold and being generated for each spectral resource block; and the second base station transmits said downlink transmission power control information to said first base station via backhaul communication .

The communication methods and associated base stations according to the present invention have the advantages of simple implementation and high system throughput.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects , features and advantages of the present invention will be more apparent from the following preferred embodiments illustrated with reference to the figures, in which :

Fig. 1 is a schematic diagram of a MIMO system;

Fig. 2 a schematic diagram of a multi-cell cellular communication system;

Fig. 3 is a schematic diagram of a communication method according to the first aspect of the present invention;

Fig. 4 is a schematic diagram of a communication method according to the second aspect of the present invention;

Fig. 5 is a schematic diagram of a service area formed by adjacent BS 200 and BS 300 ;

Fig. 6 is a schematic diagram of a service area formed by adj acent BS 100 and BS 200 ;

Fig. 7 is a schematic diagram of a BS according to the first aspect of the present invention;

Fig. 8 is a schematic diagram of a BS according to the second aspect of the present invention ;

Fig. 9 is a schematic diagram of a communication method according to the third aspect of the present invention;

Fig. 10 is a schematic diagram of a communication method according to the fourth aspect of the present invention;

Fig. 1 1 is a schematic diagram of a BS according to the third aspect of the present invention; and

Fig. 12 is a schematic diagram of a BS according to the fourth aspect of the present invention .

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will be detailed with reference to the drawings. In the following description, details and functions unnecessary to the present invention are omitted so as not to obscure the concept of the invention .

For clear and detailed explanation of the implementation of the present invention, some specific examples applicable to the LTE-A (Rel- 10 , Rel- 1 1 and subsequent releases) cellular communication system are given below. Herein, it is to be noted that the present invention is not limited to the application exemplified in the embodiments . Rather, it is applicable to other communication systems, such as the future 5G system.

Fig. 2 illustrates an LTE-A Rel- 1 1 network in scenario 4.

The cellular system divides a service coverage area into a number of adj acent wireless coverage areas, i . e. , cells. In Fig. 2 , the entire service area is formed by cells A, B and C, each being illustratively shown as a hexagon. BS 200 , BS 202 and BS 204 are associated with the cells A, B and C , respectively. As known to those skilled in the art, each of the BS 200, BS 202 and BS 204 includes at least a transmitter and a receiver. As illustratively shown in Fig. 2 , each of the BS 200 , BS 202 and BS 204 is located in a particular area of the corresponding one of the cells A, B and C and is equipped with an omni-directional antenna. However, in a cell arrangement for the cellular communication system, each of the BS 200 , BS 202 and B S 204 can also be equipped with a directional antenna for directionally covering a partial area of the corresponding one of the cells A, B and C , which is commonly referred to as a sector. Thus, the diagram of the multi-cell cellular communication system as shown in Fig. 2 is illustrative only and does not imply that the implementation of the cellular system according to the present invention is limited to the above particular constraints.

As shown in Fig. 2 , in the area covered by BS 200, there are five distributed RRUs, respectively denoted as R 202 , R 204 , R 206, R 208 and R 2 10. All the six transmission points including BS 200 and R 202 - R 2 10 have the same cell ID . The five distributed RRUs have different sub-IDs. In the area covered by BS 100, there are three distributed RRUs, respectively denoted as R 102 , R 104 and R 106. All the four transmission points including BS 100 and R 102 - R 106 have the same cell ID . In the area covered by BS 300, there are two distributed RRUs, respectively denoted as R 302 and R 304. All the four transmission points including BS 300 and R 302 - R 304 have the same cell ID . All RRUs are respectively connected to corresponding BSs via optical fibers, denoted with dash lines in Fig. 2.

As shown in Fig. 2 , the BS 100 , BS 200 and BS 300 are connected with each other via X2 interfaces BH 400 , BH 402 and BH 404 , denoted with dash-dot lines in Fig. 2. In a LTE-A system, a three-layer node network architecture including base station , radio network control unit and core network is simplified into a two-layer node architecture in which the function of the radio network control unit is assigned to the base station and a wired interface named "X2" is defined for coordination and communication between base stations . It should be noted that, in a future communication system, there may also exist a wireless interface between BSs for coordination and communication. Interfaces BH 400 , BH 402 and BH 404 just exemplify the communication medium between BSs. Such a medium may take the form of a wired communication network complying with various communication standards, such as IPv4 , IPv6, etc.

In the following, a fundamental solution enabling data muting in the multi-antenna multi-BS coordination scenario 4 will be given with reference to Fig. 3 and Fig. 4. For simplicity, it is only described how to implement this solution with respect to adjacent BS 200 and BS 300. In Fig. 5, a service area formed by adjacent BS 200 and BS 300 is illustrated .

Now, a process performed by BS 300 will be described with reference to Fig. 3. As shown in Fig. 3 , at step S30 1 , BS 300 receives data muting information from BS 200. The data muting information corresponds to the directionally communicated information DS 700 transmitted from BS 200 to BS 300 as shown in Fig. 5, and contains at least an identity (ID) of BS 300 and an indication indicative of positions for data muting. The ID of BS 300 is used to carry out functions, such as message routing and the like . The indication may be positional information of CSI-RSs of one or more RRUs geographically closer to BS 300 (i. e . , R 208 and/ or R2 10) , or positional information of CSI-RSs of BS 200 and RRUs geographically closer to BS 300 (i. e . , R 208 and/ or R2 10) . The data muting information can be generated and transmitted according to a method that will be described later with reference to Fig. 4. Next, at step S302, BS 300 performs data muting according to the indication. Specifically, data muting may be performed at positions of CSI-RSs of RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), or at positions of CSI-RSs of BS 200 and RRUs geographically closer to BS 300 (i.e., R 208 and/or R210).

It should be noted that, if the indication indicates positions of CSI-RSs of RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), the directionally communicated information DS 700 may further contain sub-IDs of the one or more RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), so that BS 300 can choose an optimal data muting strategy. For example, when resources available to BS 300 are insufficient, BS 300 may choose to mute its data transmission only at positions of CSI-RSs of R 208 or R 210. As another example, BS 300 may perform resource scheduling to limit downlink transmission of RRU (e.g. R 302) closer to R 208 and/or R 210, so as to mute R 302's data transmission at positions of CSI-RSs of R 208 or R 210; while, as for R 304 which is far from R 208 and/or R 210, BS 300 may not mute its data transmission, so that users around R 304 may enjoy better quality of service.

If the indication indicates positions of CSI-RSs of BS 200 and RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), the directionally communicated information may further contain an ID of BS 200 and/or sub-IDs of the one or more RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), so that BS 300 can choose an optimal data muting strategy. For example, when resources available to BS 300 are insufficient, BS 300 may choose to mute its data transmission only at positions of CSI-RSs of BS 200 or R 208 or R 210. As another example, BS 300 may perform resource scheduling to limit downlink transmission of RRU (e.g. R 302), which is closer to BS 200 and/or RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), so as to mute R 302's data transmission at positions of CSI-RSs of BS 200 and/or RRUs geographically closer to BS 300 (i.e., R 208 and/or R210); while, as for R 304 which is far from BS 200 and/or RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), BS 300 may not mute its data transmission, so that users around R 304 may enjoy better quality of service.

Now, a process performed by BS 200 will be described with reference to Fig.4. The process starts from step S401, wherein data muting information is generated. As described above, the data muting information contains at least an identity (ID) of BS 300 that heavily interferes with BS 200 and an indication indicative of positions for data muting.

There are many manners for BS 200 to determine BSs heavily interfering with itself and to obtain IDs of these BSs. According to the principle that a signal attenuates as it travels, the simplest manner is to determine BS 200 's neighboring BSs as BSs heavily interfering with BS 200. Because BSs and RRUs, as part of the infrastructure, are generally fixed apparatuses, IDs of neighboring BSs can be obtained in advance by looking up a network planning table. Specifically, considering BS 300 is adj acent to BS 200 as shown in Fig. 5 , the data muting information contains the ID of BS 300.

Furthermore, when configuring RRUs, BS 200 may learn that, among five RRUs (R 202 - R 2 10) under its control, R 208 and R 2 10 are geographically closer to BS 300. Therefore , it is necessary to require BS 300 to keep CSI-RSs of R 208 and R 2 10 uninfluenced, i.e . , to require BS 300 to mute its data transmission at positions of CSI -RSs of R 208 and R 2 10. Thus , the data muting information contains positional information of CSI-RSs of R 208 and R 2 10. Certainly, the data muting information may also contain positional information of CSI-RSs of BS 200 geographically closer to BS 300.

Moreover, sub-IDs of R 208 and R2 10 are known to BS 200. Therefore, as described with reference to Fig. 3 , the data muting information may further contain sub-IDs of one or more RRUs geographically closer to BS 300 (i. e. , R 208 and / or R 2 10) . Certainly, the data muting information may contain the ID of BS 200.

Subsequently, at step S402 , via the backhaul communication link BH 402 , BS 200 transmits the data muting information generated at step S401 (i.e . the directionally communicated information DS 700 as shown in Fig. 5) to BS 300.

In the following, it will be described how to implement the inventive solution with respect to adjacent BS 200 and BS 100. In Fig. 6, a service area formed by adj acent BS 200 and BS 100 is illustrated.

Because BSs and RRUs , as part of the infrastructure, are generally fixed apparatuses, a BS can obtain neighboring BSs' IDs in advance by looking up a network planning table . As for BS 200 , its neighboring BS is BS 100. When configuring RRUs, BS 200 may learn that, among five RRUs (R 202 - R 2 10) under its control, R 204 is geographically closer to BS 100 and thus suffers from heavier interference from BS 100. Therefore , it is necessary to require BS 100 to keep CSI-RSs of R 204 uninfluenced, i . e . , to require BS 100 to mute its data transmission at positions of CSI- RSs of R 204. Thus, the directionally communicated information transmitted from BS 200 to BS 100 via the backhaul communication link BH 400 contains at least the ID of the target BS 100 and an indication indicative of positions for data muting. The indication may be positional information of CSI-RSs of R 204 and optionally may be information on the period of CSI-RSs of R 204. In Fig. 6 wherein the embodiment is illustrated, DS 702 corresponds to the directionally communication information . It should be noted that the directionally communication information may further contain the sub-ID of R 204 , so that BS 100 can choose an optimal data muting strategy. For example, when resources available to BS 100 are insufficient, BS 100 may limit downlink transmission of RRU (e . g. R 102 , R 106) closer to R 204 , so as to mute data transmission of R 102 , R 106 at positions of CSI-RSs of R 204 ; while, as for R 104 which is far from R 204 , BS 100 may not mute its data transmission, so that users around R 104 may enj oy better quality of service .

Furthermore, when configuring RRUs, BS 200 may learn that, among five RRUs (R 202 - R 2 10) under its control, R 204 and BS 200 itself are geographically closest to BS 300, and thus may suffer from heavier interference from BS 100. Therefore , it is necessary to require BS 100 to keep CSI-RSs of R 204 and BS 200 uninfluenced, i. e . , to require BS 100 to mute its data transmission at positions of CSI-RSs of R 204 and BS 200. Thus, the directly communicated information transmitted from BS 200 to BS 100 via the backhaul communication link BH 400 contains at least the ID of the target BS 100 and an indication indicative of positions for data muting. The indication may be positional information of CSI-RSs of R 204 and BS 200 and optionally may be information on the periods of CSI-RSs of R 204 and BS 200. In Fig. 6 wherein the embodiment is illustrated, DS 702 corresponds to the directionally communication information. It should be noted that the directionally communication information may further contain the sub-ID of R 204 and/ or the ID of BS 200, so that BS 100 can choose an optimal data muting strategy. For example, when resources available to BS 100 are insufficient, BS 100 may choose to mute its data transmission only at positions of CSI-RS s of R 208 or R 2 10. As another example, BS 100 may perform resource scheduling to limit downlink transmission of RRU (e .g. R 1 02 , R 106) closer to R 204 and / or BS 200 , so as to mute data transmission of R 102 , R 106 at positions of CSI-RSs of R 204 and / or BS 200 ; while , as for R 104 which is far from R 204 and/ or BS 200, BS 100 may not mute R 104 's data transmission, so that users around R 104 may enj oy better quality of service .

(Hardware implementation enabling data muting in scenario 4) Now, base stations 700 and 800 according to the first and second aspects of the present invention will be described with respect to Figs . 7 and 8, respectively. In the schematic diagram of Fig. 5, BS 300 constitutes the base station 700 and BS 200 constitutes the base station 800. In the schematic diagram of Fig. 6, BS 100 constitutes the base station 700 and BS 200 constitutes the base station 800.

As shown in figure 7, the base station 700 comprises: a reception unit 7 10 configured to receive data muting information from the base station 800 via backhaul communication, wherein the data muting information contains an ID of the base station 700 and a positional indication for data muting; and a muting unit 720 configured to perform data muting at positions indicated by the positional indication for data muting. The positional indication for data muting indicates positions of CSI-RSs of one or more RRU s, located in a cell range of the base station 800 , whick are closest to the base station 700. The positional indication may further indicate positions of CSI- RSs of the base station 800.

If the data muting information further contains sub-IDs of the above-mentioned one or more RRUs located in the cell range of the base station 800 , the muting unit 720 may selectively perform data muting at the positions of CSI-RSs of the above-mentioned one or more RRUs located in the cell range of the base station 800. Also, the base station 700 may further comprise a resource scheduling unit 730 configured to cause one or more RRUs located in a cell range of the base station 700 to perform data muting, said one or more RRUs located in the cell range of the base station 700 being closest to the above-mentioned one or more RRUs located in the cell range of the base station 800.

Alternatively, if the data muting information further contains an ID of the base station 800 and / or sub-IDs of the above-mentioned one or more RRUs located in the cell range of the base station 800 , the muting unit 720 may selectively perform data muting at the positions of CSI-RSs of the base station 800 and the above-mentioned one or more RRUs located in the cell range of the base station 800. Also, the resource scheduling unit 730 may be configured to cause one or more RRUs located in the cell range of the base station 700 to perform data muting, said one or more RRUs located in the cell range of the base station 700 being closest to the base station 800 and/ or the above-mentioned one or more RRUs in the cell range of the base station 800.

As shown in Fig. 8 , the base station 800 comprises: a data muting information generation unit 8 10 configured to generate data muting information, which contains an ID of the first base station 700 and a positional indication for data muting; and a transmission unit 820 configured to transmit the data muting information to the base station 700 via backhaul communication .

In the following, a fundamental solution enabling downlink power control in the multi-antenna multi-BS coordination scenario 4 will be given with reference to Fig. 9 and Fig. 10. For simplicity, it is only described how to implement this solution with respect to adj acent BS 200 and BS 300. In Fig. 5 , a service area formed by adj acent BS 200 and BS 300 is illustrated .

Now, a process performed by BS 300 will be described with reference to Fig. 9. As shown in Fig. 9 , at step S90 1 , BS 300 receives downlink transmission power control information from BS 200. The downlink transmission power control information corresponds to the directionally communicated information DS 700 transmitted from BS 200 to BS 300 as shown in Fig. 5, and contains at least an identity (ID) of BS 300 and a transmission power indication reported on per spectral resource block basis . Optionally, the transmission power indication may further contain specific transmission power thresholds, which may be transmission power thresholds of one or more RRUs geographically closer to BS 300 (i. e . , R 208 and/ or R 2 10) , or transmission power thresholds of BS 200 and one or more RRUs geographically closer, to BS 300 (i. e . , R 208 and / or R 2 10) . Accordingly, the transmission power indication may indicate whether transmission powers of one or more RRUs geographically closer to BS 300 (i.e . , R 208 and / or R 2 10) exceed respective transmission power thresholds, or indicate whether transmission powers of BS 200 and one or more RRUs geographically closer to BS 300 (i. e . , R 208 and/ or R 2 10) exceed respective transmission power thresholds . The downlink transmission power control information can be generated and transmitted according to a method that will be described later with reference to Fig. 10.

Next, at step S902 , BS 300 takes a resource scheduling measure or the like according to the indication, so as not to assign a UE vulnerable to interference to a spectral resource block, for which it is indicated that the respective transmission power thresholds are exceeded and thus which suffers from heavy interference.

It should be noted that, if the indication indicates whether the transmission powers of one or more RRUs geographically closer to BS 300 (i.e., R 208 and/or R 210) exceed the respective transmission power thresholds, the directionally communicated information DS 700 may further contain sub-IDs of the one or more RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), so that BS 300 can choose an optimal strategy for handling interference. For example, BS 300 may determine that R 302 is closer to R 208 and/or R210 and may thus take a rigorous measure for R 302 to cope with interference (for example, by scheduling to serve only those users located at the center of the area covered by R 302, with spectral resources on which transmission powers of R 208 and/or R210 are higher, so as to alleviate effect of interference); while for R 304 which is far from R 208 and/or R210, BS 300 may take a less rigorous measure to copy with interference, so that scheduling can be performed more flexibly for R 304.

If the indication indicates whether the transmission powers of BS 200 and one or more RRUs geographically closer to BS 300 (i.e., R 208 and/or R 210) exceed the respective transmission power thresholds, the directionally communicated information may further contain an ID of BS 200 and/or sub-IDs of the one or more RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), so that BS 300 can choose an optimal strategy for handling interference. For example, BS 300 may determine that R 302 is closer to BS 200 and/or RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), and may thus take a rigorous measure for R 302 to cope with interference (for example, by scheduling to serve only those users located at the center of the area covered by R 302, with spectral resources on which transmission powers of BS 200 and/or R 208 and/or R210 are higher, so as to alleviate effect of interference); while for R 304 which is far from BS 200 and/or RRUs geographically closer to BS 300 (i.e., R 208 and/or R210), BS 300 may take a less rigorous measure to copy with interference, so that scheduling can be performed more flexibly for R 304.

Now, a process performed by BS 200 will be described with reference to Fig. 10. The process starts from step S1001, wherein downlink transmission power control information is generated. As described above, the downlink transmission power control information contains at least an ID of BS 300 suffering from BS 200's interference and a transmission power indication.

There are many manners for BS 200 to determine BSs suffering from its interference and to obtain IDs of these BSs. According to the principle that a signal attenuates as it travels, the simplest manner is to determine BS 200 's neighboring BSs as BSs suffering from BS 200 's interference . Because BSs and RRUs, as part of the infrastructure, are generally fixed apparatuses, IDs of neighboring BSs can be obtained in advance by looking up a network planning table . Specifically, considering BS 300 is adj acent to BS 200 as shown in Fig. 5 , the downlink transmission power control information contains the ID of BS 300.

Furthermore, when configuring RRUs, BS 200 may learn that, among five RRUs (R 202 - R 2 10) under its control, R 208 and R 2 10 are geographically closer to BS 300 and may heavily interfere with BS 300. Therefore , it is necessary to report, on per spectral resource block basis, a transmission power indication to BS 300 , indicating for each spectral resource block whether the transmission powers of R 208 and R 2 10 exceed preset thresholds . Thus, the downlink transmission power control information contains the indication indicating whether the transmission powers of R 208 and R 2 10 exceed the preset thresholds . Certainly, the downlink transmission power control information may also contain an indication indicating whether the transmission power of BS 200 geographically closer to BS 300 exceeds a preset threshold.

Moreover, sub-ID s of R 208 and R2 10 are known to BS 200. Therefore, as described with reference to Fig. 9 , the downlink transmission power control information may further contain sub-IDs of one or more RRUs geographically closer to BS 300 (i. e . , R 208 and/ or R 2 10) . Certainly, the downlink transmission power control information may also contain the ID of BS 200.

Subsequently, at step S 1002 , via the backhaul communication link BH 402 , BS 200 transmits the downlink transmission power control information generated at step S 100 1 (i.e . the directionally communicated information DS 700 as shown in Fig. 5) to BS 300.

In the following, it will be described how to implement the inventive solution with respect to adj acent BS 200 and BS 100. In Fig. 6, a service area formed by adjacent BS 200 and BS 1 00 is illustrated.

Because BSs and RRUs, as part of the infrastructure, are generally fixed apparatuses, a BS can obtain neighboring BSs' IDs in advance by looking up a network planning table . As for BS 200, its neighboring BS is BS 100. When configuring RRUs, BS 200 may learn that, among five RRUs (R 202 - R 2 10) under its control, R 204 is geographically closer to BS 1 00 and may heavily interfere with BS 1 00. Therefore, it is necessary to report, on per spectral resource block basis, a transmission power indication to BS 300 , indicating for each spectral resource block whether the transmission power of R 204 exceed a preset threshold . Upon reception of the transmission power indication, BS 100 may take a resource scheduling measure or the like, so as not to assign a UE vulnerable to interference to a spectral resource block suffering from heavy interference . Especially, for R 102 and R 106 in BS 100 's cell range , measures should be taken to cope with interference from R 204. Thus , the directionally communicated information transmitted from BS 200 to BS 100 via the backhaul communication link BH 400 contains at least the ID of the target BS 100 and an indication indicating for each spectral resource block whether transmission powers thereon exceed respective transmission power thresholds . Optionally, the directionally communicated information may further contain the respective transmission power thresholds. In Fig. 6 wherein the embodiment is illustrated, DS 702 corresponds to the . directionally communication information.

It should be noted that the directionally communication information may further contain the sub-ID of R 204 , so that BS 100 can choose an optimal strategy for handling interference . For example, BS 100 may determine that R 102 and/ or R 106 are closer to R 204 and may thus take a rigorous measure for R 102 and/ or R 106 to cope with interference (for example, by scheduling to serve only those users located at the centers of the areas covered by R 102 and/ or R 106, with spectral resources on which transmission power of R 204 is higher, so as to alleviate effect of interference) ; while for R 104 which is far from R 204 , BS 100 may take a less rigorous measure to copy with interference, so that scheduling can be performed more flexibly for R 104.

Furthermore, when configuring RRUs, BS 200 may learn that, among five RRUs (R 202 - R 2 10) under its control, R 204 and BS 200 itself are geographically closest to BS 300 , and thus may heavily interfere with BS 100. Therefore, it is necessary to report, on per spectral resource block basis , a transmission power indication to BS 100, indicating for each spectral resource block whether the transmission powers of R 204 and BS 200 exceed preset thresholds . Upon reception of the transmission power indication, BS 100 may take a resource scheduling measure or the like , so as not to assign a UE vulnerable to interference to a spectral resource block suffering from heavy interference . Especially, for R 1 02 and R 106 in BS 100's cell range, measures should be taken to cope with interference from R 204 and BS 200. Thus, the directionally communicated information transmitted from BS 200 to BS 1 00 via the backhaul communication link BH 400 contains at least the ID of the target BS 100 and an indication indicating for each spectral resource block whether transmission powers thereon exceed respective transmission power thresholds . In Fig. 6 wherein the embodiment is illustrated, DS 702 corresponds to the directionally communication information.

It should be noted that the directionally communication information may further contain the sub-ID of R 204 and/ or the ID of BS 200 , so that BS 100 can choose an optimal strategy for handling interference . For example , BS 100 may determine that R 102 and/ or R 106 are closer to R 204 and/ or BS 200 and may thus take a rigorous measure for R 102 and/ or R 106 to cope with interference (for example, by scheduling to serve only those users located at the centers of the areas covered by R 102 and/ or R 106, with spectral resources on which transmission powers of R 204 and/ or BS 200 are higher, so as to alleviate effect of interference) ; while for R 104 which is far from R 204 and/ or BS 200, BS 100 may take a less rigorous measure to copy with interference, so that scheduling can be performed more flexibly for R 104.

(Hardware implementation enabling downlink transmission power control in scenario 4)

Now, base stations 1 100 and 1200 according to the third and fourth aspects of the present invention will be described with respect to Figs . 1 1 and 12 , respectively. In the schematic diagram of Fig. 5, BS 300 constitutes the base station 1 100 and BS 200 constitutes the base station 1200. In the schematic diagram of Fig. 6, BS 100 constitutes the base station 1 100 and BS 200 constitutes the base station 1200.

As shown in figure 1 1 , the base station 1 100 comprises: a reception unit 1 1 10 configured to receive downlink transmission power control information from the base station 1200 via backhaul communication, wherein the downlink transmission power control information contains an ID of the base station 1 100 and a transmission power indication, the transmission power indication indicating whether a transmission power exceeds a transmission power threshold and being generated on per spectral resource block basis; and a resource scheduling unit 1 120 configured to prevent a user equipment being assigned to a spectral resource block, for which it is indicated that the transmission power threshold is exceeded. The transmission power indication indicates whether transmission powers of one or more RRUs located in a cell range of the base station 1200 exceed respective transmission power thresholds, said one or more RRUs located in the cell range of the base station 1200 being closest to the base station 1 100. The transmission power indication may further indicate whether the transmission power of the base station 1200 exceeds the transmission power threshold of the base station 1200.

If the downlink transmission power control information further contains sub-IDs of the above-mentioned one or more RRUs located in the cell range of the base station 1200 , the base station 1 100 may further comprise an anti-interference measure applying unit 1 130 configured to further alleviate effect of interference, for one or more RRUs located in a cell range of the base station 1 100 , which are closest to the above-mentioned one or more RRUs in the cell range of the base station 1200.

Alternatively, if the downlink transmission power control information further contains an ID of the base station 1200 and/ or sub-IDs of the above-mentioned one or more RRUs in the cell range of the base station 1200 , the anti-interference measure applying unit 1 130 may be configured to further alleviate effect of interference, for one or more RRUs located in the cell range of the base station 1 100, which are closest to the base station 1200 and/ or the above-mentioned one or more RRUs in the cell range of the base station 1200.

As shown in Fig. 12 , the base station 1200 comprises: a downlink transmission power control information generation unit 12 10 configured to generate downlink transmission power control information, which contains an ID of the base station 1 100 and a transmission power indication, the transmission power indication indicating whether a transmission power exceeds a transmission power threshold and being generated on per spectral resource block basis ; and a transmission unit 1220 configured to transmit the downlink transmission power ^{" ""} control information to the base station 1 100 via backhaul communication .

It should be noted that the solution of the present invention has been described above by a way of example only. However, the present invention is not limited to the above steps and element structures. It is possible to adjust, add and remove the steps and elements structures depending on actual requirements . Thus, some of the steps and elements are not essential for achieving the general inventive concept of the present invention. Therefore, the features necessary for the present invention is only limited to a minimum requirement for achieving the general inventive concept of the present invention, rather than the above specific examples.

The present invention has been described above with reference to the preferred embodiments thereof. It should be understood that various modifications, alternations and additions can be made by those skilled in the art without departing from the spirits and scope of the present invention . Therefore, the scope of the present invention is not limited to the above particular embodiments but only defined by the claims as attached .

Claims

1 . A communication method, comprising the following steps:

a first base station receives data muting information from a second base station via backhaul communication, wherein said data muting information contains an identity (ID) of the first base station and a positional indication for data muting; and

the first base station performs data muting at positions indicated by said positional indication for data muting.

2. The method according to claim 1 , wherein said positional indication for data muting indicates positions of C annel State Information - Reference Signals (CSI-RSs) of one or more Remote Radio Units (RRUs) , located in a cell range of the second base station, which are closest to the first base station .

3. The method according to claim 2 , wherein said positional indication for data muting further indicates a position of CSI-RS of the second base station .

4. The method according to claim 2 , wherein said data muting information further contains sub-IDs of said one or more RRUs located in the cell range of the second base station, and

wherein said first base station selectively performs data muting at the positions of CSI-RS s of said one or more RRUs located in the cell range of the second base station; and / or said first base station causes one or more RRUs located in a cell range of the first base station to perform data muting, said one or more RRUs located in the cell range of the first base station being closest to said one or more RRUs located in the cell range of the second base station .

5. The method according to claim 3 , wherein said data muting information further contains an ID of the second base station and/ or sub-IDs of said one or more RRUs located in the cell range of the second base station, and

wherein said first base station selectively performs data muting at the positions of CSI-RSs of said one or more RRUs located in the cell range of the second base station and said second base station; and/ or

said first base station causes one or more RRUs located in a cell range of the first base station to perform data muting, said one or more RRUs located in the cell range of the first base station being closest to said second base station and / or said one or more RRUs located in the cell range of the second base station .

6. A base station, named a first base station, comprising: a reception unit configured to receive data muting information from a second base station via backhaul communication, wherein said data muting information contains an ID of the first base station and a positional indication for data muting; and

a muting unit configured to perform data muting at positions indicated by the positional indication for data muting.

7. The base station according to claim 6, wherein said positional indication for data muting indicates positions of CSI-RSs of one or more RRUs, located in a cell range of the second base station, which are closest to the first base station.

8. The base station according to claim 7, wherein said positional indication further indicates a position of CSI-RS of the second base station.

9. The base station according to claim 7 , wherein said data muting information further contains sub-IDs of said one or more RRUs located in the cell range of the second base station, and

wherein said muting unit selectively performs data muting at the positions of CSI-RSs of said one or more RRUs located in the cell range of the second base station; and / or

said first base station further comprises a resource scheduling unit configured to cause one or more RRUs located in a cell range of the first base station to perform data muting, said one or more RRUs located in the cell range of the first base station being closest to said one or more RRUs located in the cell range of the second base station .

10. The base station according to claim 8 , wherein said data muting information further contains an ID of the second base station and/ or sub-IDs of said one or more RRUs located in the cell range of the second base station, and

wherein said muting unit selectively performs data muting at the positions of CSI-RSs of said one or more RRUs located in the cell range of the second base station and said second base station; and/ or

said first base station further comprises a resource scheduling unit configured to cause one or more RRUs located in a cell range of the first base station to perform data muting, said one or more RRUs located in the cell range of the first base station being closest to said second base station and/ or said one or more RRUs located in the cell range of the second base station .

1 1 . A communication method, comprising the following steps:

a second base station generates data muting information, which contains an ID of a first base station and a positional indication for data muting; and

the second base station transmits said data muting information to said first base station via backhaul communication.

12. The method according to claim 1 1 , wherein said positional indication for data muting indicates positions of CSI-RSs of one or more RRUs, located in a cell range of the second base station, which are closest to the first base station .

13. The method according to claim 12 , wherein said positional indication for data muting further indicates a position of C SI-RS of the second base station .

14. The method according to claim 12 , wherein said data muting information further contains sub-IDs of said one or more RRUs located in the cell range of the second base station.

1 5. The method according to claim 13 , wherein said data muting information further contains an ID of the second base station and/ or sub-IDs of said one or more RRUs located in the cell range of the second base station.

16. A base station, named a second base station, comprising:

a data muting information generation unit configured to generate data muting information, which contains an ID of a first base station and a positional indication for data muting; and

a transmission unit configured to transmit said data muting information to said first base station via backhaul communication .

17. The base station according to claim 16, wherein said positional indication for data muting indicates positions of CSI-RSs of one or more RRUs, located in a cell range of the second base station, which are closest to the first base station.

18. The base station according to claim 17 , wherein said positional indication for data muting further indicates a position of CSI-RS of the second base station .

19. The base station according to claim 17 , wherein said data muting information further contains sub-IDs of said one or more RRUs located in the cell range of the second base station .

20. The base station according to. claim 18, wherein said data muting information further contains an ID of the second base station and / or sub-IDs of said one or more RRUs located in the cell range of the second base station.

2 1 . A communication method, comprising the following steps:

a first base station receives downlink transmission power control information from a second base station via backhaul communication, wherein said downlink transmission power control information contains an ID of the first base station and a transmission power indication , said transmission power indication indicating whether a transmission power exceeds a transmission power threshold and being generated on per spectral resource block basis; and

the first base station performs resource scheduling so as to prevent a user equipment from being assigned to a spectral resource block for which said transmission power indication indicates that the transmission power threshold is exceeded .

22. The method according to claim 2 1 , wherein said transmission power indication indicates whether transmission powers of one or more RRUs located in a cell range of the second base station exceed respective transmission power thresholds , said one or more RRUs located in the cell range of the second base station being closest to the first base station .

23. The method according to claim 22 , wherein said transmission power indication further indicates whether the transmission power of the second base station exceeds the transmission power threshold of the second base station.

24. The method . according to claim 22 , wherein said downlink transmission power control information further contains sub-IDs of said one or more RRUs located in the cell range of the second base station, and

wherein said first base station takes further anti-interference measure, for one or more RRUs located in a cell range of the first base station, which are closest to said one or more RRUs located in the cell range of the second base station.

25. The method according to claim 23 , wherein said downlink transmission power control information further contains an ID of the second base station and / or sub-IDs of said one or more RRUs located in the cell range of the second base station, and

wherein said first base station takes further anti-interference measure , for one or more RRUs located in a cell range of the first base station , which are closest to said second base station and/ or said one or more RRUs located in the cell range of the second base station .

26. A base station, named a first base station, comprising: a reception unit configured to receive downlink transmission power control information from a second base station via backhaul communication, wherein said downlink transmission power control information contains an ID of the first base station and a transmission power indication, said transmission power indication indicating whether a transmission power exceeds a transmission power threshold and being generated on per spectral resource block basis; and a resource scheduling unit configured to prevent a user equipment from being assigned to a spectral resource block for which said transmission power indication indicates that the transmission power threshold is exceeded .

27. The base station according to claim 26, wherein said transmission power indication indicates whether transmission powers of one or more RRUs located in a cell range of the second base station exceed respective transmission power thresholds, said one or more RRUs located in the cell range of the second base station being closest to the first base station .

The base station according to claim 27, wherein said transmission power indication further indicates whether the transmission power of the second base station exceeds the transmission power threshold of the second base station .

29. The base station according to claim 27, wherein said downlink transmission power control information further contains sub-IDs of said one or more RRUs located in the cell range of the second base station, and

wherein said first base station further comprises an anti-interference measure applying unit configured to further alleviate effect of interference, for one or more RRUs located in a cell range of the first base station, which are closest to said one or more RRUs located in the cell range of the second base station .

30. The base station according to claim 28, wherein said downlink transmission power control information further contains an ID of the second base station and / or sub-IDs of said one or more RRUs located in the cell range of the second base station, and

wherein said first base station further comprises an anti-interference measure applying unit configured to further alleviate effect of interference, for one or more RRUs located in a cell range of the first base station, which are closest to said second base station and/ or said one or more located in the cell range of the second base station.

3 1 . A communication method, comprising the following step :

a second base station generates downlink transmission power control information, which contains an ID of the first base station and a transmission power indication, said transmission power indication indicating whether a transmission power exceeds a transmission power threshold and being generated on per spectral resource block basis; and the second base station transmits said downlink transmission power control information to said first base station via backhaul communication .

32. The method according to claim 3 1 , wherein said transmission power indication indicates whether transmission powers of one or more RRUs located in a cell range of the second base station exceed respective transmission power thresholds, said one or more RRUs located in the cell range of the second base station being closest to the first base station .

33. The method according to claim 32 , wherein said transmission power indication further indicates whether the transmission power of the second base station exceeds the transmission power threshold of the second base station .

34. The method according to claim 32 , wherein said downlink transmission power control information further contains sub-IDs of said one or more RRUs located in the cell range of the second base station.

35. The method according to claim 33 , wherein said downlink transmission power control information further contains an ID of the second base station and/ or sub-IDs of said one or more RRUs located in the cell range of the second base station.

36. A base station, named a second base station , comprising:

a downlink transmission power control information generation unit configured to generate downlink transmission power control information, which contains an ID of the first base station and a transmission power indication, said transmission power indication indicating whether a transmission power exceeds a transmission power threshold and being generated on per spectral resource block basis ; and a transmission unit configured to transmit said downlink transmission power control information to said first base station via backhaul communication.

37. The base station according to claim 36, wherein said transmission power indication indicates whether transmission powers of one or more RRUs located in a cell range of the second base station exceed respective transmission power thresholds, said one or more RRUs located in the cell range of the second base station being closest to the first base station .

38. The base station according to claim 37 , wherein said transmission power indication further indicates whether the transmission power of the second base station exceeds the transmission power threshold of the second base station .

39. The base station according to claim 37 , wherein said downlink transmission power control information further contains sub-IDs of said one or more RRUs located in the cell range of the second base station.

40. The base station according to claim 38 , wherein said downlink transmission power control information further contains an ID of the second base station and/ or sub-IDs of said one or more RRUs located in the cell range of the second base station .