CN106788646B

CN106788646B - Method and apparatus for communication using virtual cell and communication system

Info

Publication number: CN106788646B
Application number: CN201510827478.6A
Authority: CN
Inventors: 佘锋; 郭海友
Original assignee: Nokia Shanghai Bell Co Ltd
Current assignee: Nokia Shanghai Bell Co Ltd
Priority date: 2015-11-24
Filing date: 2015-11-24
Publication date: 2022-03-18
Anticipated expiration: 2035-11-24
Also published as: WO2017089898A1; CN106788646A

Abstract

Various embodiments of the present disclosure provide methods and apparatus for communication and corresponding communication systems. In a communication method implemented in a macro base station, configuration information relating to UL reference signals to be transmitted by a UE is transmitted to a candidate small cell of a plurality of small cells. The configuration information is used by the candidate small cells to receive UL reference signals in order to determine channel state information, and the channel state information indicates the channel quality of the channel between the UE and each candidate small cell. The method also includes receiving channel state information satisfying a predetermined condition from at least one of the candidate small cells, and determining a virtual cell for data communication of the UE based on the received channel state information. The virtual cell is formed by one or more of the at least one candidate small cells.

Description

Method and apparatus for communication using virtual cell and communication system

Technical Field

Embodiments of the present disclosure relate generally to the field of wireless communications, and more particularly, to a method and apparatus for communicating with a virtual cell and a corresponding communication system.

Background

In recent years, the demand for services on mobile networks has been increasing. Such an increase is reflected not only in the overall traffic of the network, but also in the bit rate requirements of the individual users. To meet such demands, one possible solution is to deploy very high density networks, which may be referred to as ultra-dense networks (UDNs). For example, tens or hundreds of micro base stations or radio access nodes are deployed within the coverage area (i.e., macro cell) of one macro base station, such as a macro enb (menb). These micro base stations may include, for example, small (small) base stations, pico (pico) base stations, femto (femto) base stations, and so on. The coverage areas of these small base stations may accordingly also be referred to as small cells, pico cells, femto cells, etc. Hereinafter, base stations deployed within a macro cell are collectively referred to as "micro base stations", and cells within a macro cell are collectively referred to as "small cells".

In a UDN network, small cells can help a macro cell to perform efficient offloading, thereby meeting the overall traffic demands of the network and the bit rate demands of individual users. However, such ultra-dense networks may present some problems. One problem is that the User Equipment (UE) may be faced with very severe interference. Another problem is that due to the mobility of the UE, frequent handovers between these small cells may occur. In order to solve the above problem, a virtual cell mechanism has recently been proposed. Several small cells or wireless access points may be grouped into one virtual cell. In the communication process, one wireless access point in the virtual cell is used as a main access point and is responsible for scheduling all the small cells in the virtual cell.

In UDN networks, the discovery of small cells is important to ensure efficient offloading from macro base stations to small cells. In the virtual cell mechanism, in order to facilitate virtual cell-based data communication, discovery of a small cell and formation of a virtual cell are essential. The performance of the communication system will be greatly reduced if the delay of the discovery of the small cell and the formation of the virtual cell is large.

In current small cell discovery schemes, small cell discovery is performed based on downlink (DL, i.e. from the base station to the UE) signals. The base station or wireless access node of a small cell broadcasts a discovery signal at a certain period, and the UE discovers a potential small cell by detecting the discovery signal. However, it is difficult to improve system performance if such conventional small cell discovery schemes are employed to discover small cells in order to form virtual cells for data communication. One major problem is that the delay in finding a small cell based on a DL signal is very long due to the periodicity of the discovery signal and the measurement and reporting of the signal. Typically this delay ranges from a few hundred milliseconds to several seconds. The longer delay of small cell discovery results in a delay in the formation of virtual cells, which in turn results in a severe degradation of the performance of the entire system.

Therefore, a solution is desired to improve the discovery of small cells and the formation of virtual cells in order to facilitate data communication of user equipments in the virtual cells.

Disclosure of Invention

An object of embodiments of the present disclosure is to provide a solution for communication using virtual cells.

According to a first aspect of the present disclosure, there is provided a communication method implemented in a macro base station. The method includes transmitting configuration information relating to an Uplink (UL) reference signal to be transmitted by a User Equipment (UE) to a candidate small cell of the plurality of small cells. The configuration information is used by the candidate small cells to receive UL reference signals in order to determine channel state information, and the channel state information indicates the channel quality of the channel between the UE and each candidate small cell. The method also includes receiving channel state information satisfying a predetermined condition from at least one of the candidate small cells, and determining a virtual cell for data communication of the UE based on the received channel state information. The virtual cell is formed by one or more of the at least one candidate small cells.

According to a second aspect of the present disclosure, there is provided a communication method implemented in a micro base station of a small cell. The method includes receiving, from a macro base station, configuration information related to UL reference signals to be transmitted by a UE. The method also includes receiving, from the UE, a UL reference signal based on the configuration information to determine channel state information. The channel state information indicates a channel quality of a channel between the UE and the small cell. The method further includes transmitting the channel state information to the macro base station for use by the macro base station in determining a virtual cell for data communication of the UE when the channel state information satisfies a predetermined condition. The virtual cell is formed of at least a small cell.

According to a third aspect of the present disclosure, a communication method implemented in a UE is provided. The method comprises transmitting a UL reference signal to the candidate small cell, such that the candidate small cell receives the UL reference signal based on configuration information received from the macro base station relating to the UL reference signal for determining channel state information, and transmitting the channel state information to the macro base station when the channel state information satisfies a predetermined condition. The channel state information indicates state information of a channel between the UE and each candidate small cell.

According to a fourth aspect of the present disclosure, there is provided a communication apparatus in a macro base station. The apparatus includes a configuration information transmission unit configured to transmit configuration information related to UL reference signals to be transmitted by the UE to a candidate small cell of the plurality of small cells. The configuration information is used by the candidate small cells to receive UL reference signals in order to determine channel state information, and the channel state information indicates the channel quality of the channel between the UE and each candidate small cell. The apparatus further includes a state information receiving unit configured to receive channel state information satisfying a predetermined condition from at least one of the candidate small cells, and a virtual cell determining unit configured to determine a virtual cell for data communication of the UE based on the received channel state information. The virtual cell is formed by one or more of the at least one candidate small cells.

According to a fifth aspect of the present disclosure, there is provided a communication apparatus in a micro base station of a small cell. The apparatus includes a configuration information receiving unit configured to receive configuration information related to a UL reference signal to be transmitted by a UE from a macro base station. The apparatus also includes a state information determining unit configured to receive a UL reference signal from the UE based on the configuration information in order to determine the channel state information. The channel state information indicates a channel quality of a channel between the UE and the small cell. The apparatus further includes a state information transmitting unit configured to transmit the channel state information to the macro base station for the macro base station to use for determining a virtual cell for data communication of the UE when the channel state information satisfies a predetermined condition. The virtual cell is formed of at least a small cell.

According to a sixth aspect of the present disclosure, there is provided a communication apparatus in a UE. The apparatus includes a UL reference signal transmission unit configured to transmit a UL reference signal to the candidate small cell, to cause the candidate small cell to receive the UL reference signal based on configuration information related to the UL reference signal received from the macro base station to determine channel status information, and to transmit the channel status information to the macro base station when the channel status information satisfies a predetermined condition. The channel state information indicates state information of a channel between the UE and each candidate small cell.

According to a seventh aspect of the present disclosure, a communication system is provided. The system comprises a macro base station comprising the apparatus discussed in the fourth aspect above. The system further comprises at least one small cell micro base station, each small cell micro base station comprising the apparatus discussed in the fifth aspect above. The system further comprises a UE comprising the apparatus discussed in the sixth aspect above.

As will be understood from the following description, according to example embodiments of the present disclosure, the determination of virtual cells is based on UL reference signals transmitted by the UE in the uplink. The UE may actively transmit uplink reference signals whenever the UE has a need, e.g., when the UE moves to a new location or has data to transmit, in order to discover available small cells and discover or form a virtual cell for data communication therewith. The macro base station may provide configuration information related to the UL reference signal to the candidate small cells for use in detecting the UL reference signal. In this way, delays associated with the discovery of small cells are significantly reduced compared to previously discovering small cells based on periodically transmitted downlink discovery signals, which in turn improves overall system performance. Other benefits brought by example embodiments of the present disclosure will become apparent from the description below.

Drawings

The above and other objects, features and advantages of the embodiments of the present disclosure will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. Several embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

FIG. 1 is a schematic illustration of an example environment in which apparatus and/or methods described herein may be implemented;

FIG. 2 is a block diagram illustrating an exemplary computer system/server suitable for use to implement embodiments of the present disclosure;

fig. 3 shows a flow diagram of a communication method implemented in a macro base station according to one embodiment of the present disclosure;

fig. 4 shows a schematic diagram of a communication process between a macro base station, a micro base station and a user equipment according to one embodiment of the present disclosure;

fig. 5 shows a schematic diagram of a communication procedure between a macro base station, a micro base station and a user equipment according to another embodiment of the present disclosure;

fig. 6 shows a schematic diagram of a communication procedure between a macro base station, a micro base station and a user equipment according to yet another embodiment of the present disclosure;

figure 7 shows a block diagram of a communication device in a macro base station according to one embodiment of the present disclosure;

figure 8 shows a block diagram of a communication device in a micro base station of a small cell according to one embodiment of the present disclosure; and

fig. 9 shows a block diagram of a communication device in a UE according to one embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The principles and spirit of the present disclosure will be described with reference to a number of exemplary embodiments shown in the drawings. It should be understood that these embodiments are described merely to enable those skilled in the art to better understand and to implement the present disclosure, and are not intended to limit the scope of the present disclosure in any way.

In describing embodiments of the present disclosure, the terms "include" and its derivatives should be interpreted as being open-ended, i.e., "including but not limited to. The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment".

In the description of the embodiments of the present disclosure, a User Equipment (UE) may refer to a terminal, a Mobile Terminal (MT), a Subscriber Station (SS), a Portable Subscriber Station (PSS), a Mobile Station (MS), or an Access Terminal (AT), and some or all of the functions of the UE, terminal, MT, SS, PSS, MS, or AT may be included. The UE may be any type of mobile terminal, fixed terminal, or portable terminal including a mobile handset, station, unit, device, multimedia computer, multimedia tablet, internet node, communicator, desktop computer, laptop computer, notebook computer, netbook computer, tablet computer, Personal Communication System (PCS) device, personal navigation device, Personal Digital Assistant (PDA), audio/video player, digital camera/camcorder, positioning device, television receiver, radio broadcast receiver, electronic book device, gaming device, or any combination thereof, including accessories and peripherals of these devices, or any combination thereof. It is also contemplated that any type of interface to the user can be supported (such as "wearable" circuitry, etc.).

In the description of the embodiments of the present disclosure, the term "Base Station (BS)" is sometimes referred to as "BS/point", "wireless access node", or "transmission point" to be consistent with 3GPP terminology. It should be noted that the terms "BS/point", "node", "transmission point" and "BS" have the same meaning in this disclosure, and each of them may represent, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a Radio Head (RH), a Remote Radio Head (RRH), a relay, a low power node such as a femto base station, a pico base station, etc. The coverage area of a base station, i.e. the geographical area where it is able to provide service, is called a cell.

In the description of embodiments of the present disclosure, the term "macro base station" refers to a base station with a large coverage area, sometimes also referred to as menb (macro enb). The coverage area of a macro base station is called a macro cell. The term "micro base station" refers to a base station with a small coverage area, which also includes pico (pico) base stations, femto (femto) base stations, and the like. The coverage of a femto base station is referred to as a small cell, which also includes pico cells, femto cells, and the like. A macro base station may include a plurality of small cells in a macro cell.

Fig. 1 is a schematic diagram of an example environment 100 in which apparatus and/or methods described herein may be implemented. The example environment 100 illustrates an example portion of an ultra-dense network (UDN). As shown in fig. 1, the macro base station 110 has a geographical area 150 for serving user equipment, i.e. a macro cell 150. A plurality of small cells 160 are deployed in the macro cell 150, each served by a respective micro base station 121-. The coverage of multiple small cells may overlap. These small cells can be used to offload data communications of the macro base station, which can improve the overall throughput of the system and the data transmission bit rate of individual users.

In UDN networks, in order to reduce excessive channel interference between small cells and to avoid frequent handover of UEs between small cells, virtual cells are introduced. One virtual cell is composed of a plurality of small cells, and can communicate with user equipment as a single cell. In the example of fig. 1, the small cells served by the micro base station 121-127 form one virtual cell. The virtual cell may communicate with UE 140 as a cell. Each virtual cell may also have one primary small cell, which is responsible for data transmission scheduling, resource scheduling, etc. of the entire virtual cell, for transmitting scheduling information to other small cells in the virtual cell in order to achieve cooperative transmission. In the example of fig. 1, the small cell served by the micro base station 124 may be the primary small cell of the virtual cell.

In embodiments of the present disclosure, UE 140 can be connected to a macro base station 110 and a micro base station of a small cell, e.g., micro base station 124. That is, UE 140 has dual connectivity capability. Generally, a small cell forming a virtual cell is in an active state to provide services to UEs located within the range of the virtual cell. One or more small cells within range of the macro cell 150 may also be in a sleeping state. For example, the small cells served by micro base station 131-.

Although several small cells included in the macro cell 150 and active and sleeping small cells therein are shown in figure 1, in some other embodiments, the macro cell 150 may include more or fewer small cells, more or fewer active small cells, and more or fewer sleeping small cells. Also, although one virtual cell is shown in figure 1 as being formed in the macro cell 150, in some other embodiments, two or more virtual small cells may also be present. Furthermore, although one UE 140 is shown, in other embodiments, there may be more UEs for serving by the virtual cell shown or other virtual cells, or directly by a certain small cell or by the macro cell 150.

FIG. 2 illustrates a block diagram of an exemplary computer system/server 12 suitable for use in implementing embodiments of the present disclosure. In some embodiments, the macro base station 110, the

micro base stations

121 and 131 and 138, and the UE 140 may include one or more computer systems/servers 12, and/or one or more components of the computer systems/servers 12. The computer system/server 12 shown in FIG. 2 is only one example and should not be taken to limit the scope of use or the functionality of embodiments of the present disclosure in any way.

As shown in FIG. 2, computer system/server 12 is in the form of a general purpose computing device. The components of computer system/server 12 may include, but are not limited to: one or more processors or processing units 16, a system memory 28, and a bus 18 that couples various system components including the system memory 28 and the processing unit 16.

Bus 18 represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, such architectures include, but are not limited to, Industry Standard Architecture (ISA) bus, micro-channel architecture (MAC) bus, enhanced ISA bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus.

Computer system/server 12 typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computer system/server 12 and includes both volatile and nonvolatile media, removable and non-removable media.

System memory 28 may include computer system readable media in the form of volatile memory, such as memory 30 and/or cache 32. The computer system/server 12 may further include other removable/non-removable, volatile/nonvolatile computer system storage media. Although not shown in FIG. 2, a magnetic disk drive for reading from and writing to a removable, nonvolatile magnetic disk (e.g., a "floppy disk") and an optical disk drive for reading from or writing to a removable, nonvolatile optical disk (e.g., a CD-ROM, DVD-ROM, or other optical media) may be provided. In these cases, each drive may be connected to bus 18 by one or more data media interfaces. Memory 28 may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of embodiments of the disclosure.

A program/utility 40 having a set (at least one) of program modules 42 may be stored, for example, in memory 28, such program modules 42 including, but not limited to, an operating system, one or more application programs, other program modules, and program data, each of which examples or some combination thereof may comprise an implementation of a network environment. Program modules 42 generally perform the functions and/or methods of the described embodiments of the present disclosure.

The computer system/server 12 may also communicate with one or more external devices (e.g., display device 24, storage device 14, etc.), with one or more devices that enable a user to interact with the computer system/server 12, and/or with any devices (e.g., network card, modem, etc.) that enable the computer system/server 12 to communicate with one or more other computing devices, as desired. Such communication may be through an input/output (I/O) interface 22. Also, the computer system/server 12 may communicate with one or more networks (e.g., a Local Area Network (LAN), a Wide Area Network (WAN) and/or a public network, such as the Internet) via the network adapter 20. As shown, network adapter 20 communicates with the other modules of computer system/server 12 via bus 18. It should be appreciated that although not shown in the figures, other hardware and/or software modules may be used in conjunction with the computer system/server 12, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems, among others.

Embodiments of the present disclosure will be described in detail below. Embodiments of the present disclosure provide a solution for communicating with a virtual cell. The solution discovers small cells based on Uplink (UL) reference signals transmitted by the UE and determines virtual cells for data communication of the UE. The formation of the virtual cell may be based on the discovered small cell. The solution involves operations performed in a macro base station of a macro cell in which the UE is located, a micro base station of a small cell that may be used to form a virtual cell, and the UE.

Referring first to fig. 3, a flow diagram of a communication method 300 of the present disclosure is described from the perspective of a macro base station. Although fig. 3 shows example blocks of the method 300, in some embodiments, the method 300 may include additional blocks, fewer blocks, different blocks, or blocks arranged differently than those depicted in fig. 3. Additionally or alternatively, two or more blocks of method 300 may be performed in parallel. In some embodiments, the method 300 may be performed by, for example, the macro base station 110 in fig. 1. The coverage of a macro base station comprises a plurality of small cells (or wireless access nodes of small cells).

As shown in fig. 3, the method 300 includes transmitting, by a macro base station, configuration information related to UL reference signals to be transmitted by a UE to a candidate small cell of a plurality of small cells in step 310. In some embodiments, the configuration information is transmitted to a wireless access node of the candidate small cell. In some embodiments, the UE is in the range of a macro cell of a macro base station and has established a connection with the macro base station.

According to embodiments of the present disclosure, a UE may broadcast a UL reference signal when, for example, it moves to a new area and/or there is data traffic to transmit in anticipation of obtaining a cell for data communication. In some embodiments, the UL reference signal may include a sounding reference signal (sounding reference signal). In other embodiments, the UE may also transmit other reference signals. In a virtual cell mechanism based network, a macro base station coordinates a plurality of small cells within its coverage area to determine therefrom a virtual cell for data communication of a UE.

In order to determine whether a certain small cell is suitable for forming a virtual cell for serving a UE, an important factor is the channel quality of a channel between the small cell and the UE, e.g. an UL channel. The small cell may receive an UL reference signal from the UE and measure Channel State Information (CSI) indicating a channel quality between the two based on the UL reference signal. To enable the small cell to receive the UL reference signal from the UE, the macro base station may send configuration information related to the UL reference signal to the small cell. The small cell receives the UL reference signal based on the configuration information. In some embodiments, the configuration information related to the UL reference signal may include, but is not limited to, a transmission period of the UL reference signal, a time-frequency location of the transmission, information related to decoding of the UL reference signal, and the like. In some embodiments, the UE has established a connection with the macro base station, and thus the macro base station may know this configuration information in advance.

In the embodiments of the present disclosure, before transmitting configuration information related to UL reference signals, the macro base station may further determine some candidate small cells that can potentially serve the UE from among a plurality of small cells within the range of the macro cell, and transmit configuration information of UL reference signals only to the determined candidate small cells. Therefore, the candidate small cell refers to a virtual cell that may form data communication to be used for the UE among a plurality of small cells covered by the macro cell. In some embodiments, the candidate small cells may include small cells that are sleeping, i.e., those not used to form a virtual cell. In these embodiments, the macro base station may know the location of the UE and determine sleeping small cells that are a close distance (e.g., within a predetermined threshold) from the UE as candidate small cells. Alternatively or additionally, the candidate small cells may comprise small cells of the formed virtual cells. In this case, the macro base station may determine, from the location of the UE, that the UE is located within the coverage of the formed virtual cell, and use the small cell forming the virtual cell as a candidate small cell. In some other embodiments, the macro base station may determine all small cells within the range of the macro cell as candidate small cells. The scope of the presently disclosed subject matter is not limited in this respect.

There may be three different scenarios based on the location of the UE and the case of small cells within the range of the macro cell. A first possible scenario is that the UE moves to an area where no virtual cell exists. In other words, in this area, small cells around the UE are all in a sleeping state. A second possible scenario is that the UE moves to an area where there are already formed virtual cells. A third possible scenario is that the UE is located in an area where there are both formed virtual cells and one or more sleeping small cells. These three possible scenarios will be discussed in detail below.

The method 300 proceeds to step 320, where the macro base station receives channel state information, CSI, satisfying a predetermined condition from at least one of the candidate small cells.

As mentioned previously, each candidate small cell, upon receiving configuration information related to the UL reference signal, may receive the UL reference signal broadcast by the UE based on the configuration information and then estimate the channel quality (i.e., channel state information) of the channel between the candidate small cell and the UE. In some embodiments, the CSI may include the strength of the UL reference signal received by the candidate small cell. For example, the CSI may be represented by one or more of a Reference Signal Received Power (RSRP), a Reference Signal Received Quality (RSRQ), or a Channel Quality Indicator (CQI). Due to the different distance between each candidate small cell and the UE or different link conditions, the CSI measured by each candidate small cell may be different. In some embodiments, if the CSI determined by one candidate small cell meets a predetermined condition, e.g., RSRP or RSRQ is above a predetermined threshold, the candidate small cell may feed back the determined CSI to the macro base station.

After receiving the CSI fed back by the one or more candidate small cells, in step 330 of the method 300, the macro base station determines a virtual cell for data communication of the UE based on the received CSI. In some embodiments, the macro base station may make decisions regarding the virtual cells based on some predetermined policies. In some embodiments, the macro base station may also transmit information related to the virtual cell to the UE and the small cell in the virtual cell to facilitate data communication between the UE and the virtual cell. According to embodiments of the present disclosure, the virtual cell determined by the macro base station may be formed by one or more of the candidate small cells from which the CSI is received. Based on the different scenarios mentioned above, the virtual cells determined by the macro base station may be different.

As can be seen from the above description, the determination of the virtual cells is based on the UL reference signals transmitted by the UE in the uplink. The UE may actively transmit uplink reference signals whenever the UE has a need, e.g., when the UE moves to a new location or has data to transmit, in order to discover available small cells and discover or form a virtual cell for data communication therewith. The macro base station may provide configuration information related to the UL reference signal to the candidate small cells for use in detecting the UL reference signal. In this way, delays associated with the discovery of small cells are significantly reduced compared to previously discovering small cells based on periodically transmitted downlink discovery signals, which in turn improves overall system performance.

Fig. 4 shows a schematic diagram of a communication process 400 in the first scenario described above, i.e. a scenario where the UE is located in an area where no virtual cell exists. This procedure involves the UE in question, the macro base station of the macro cell in which the UE is located, and the micro base stations of sleeping small cells around the UE.

In step S1, the macro base station transmits configuration information about the UL reference signal to be transmitted by the UE to each sleeping micro base station. In some embodiments, the sleeping micro base station concerned comprises a base station of a small cell that is within range of the macro cell and that is determined by the macro base station to be a candidate small cell. For example, the sleeping micro base stations include micro base stations that are within a predetermined threshold of distance from the UE and are in a sleep state. In some embodiments, the configuration information related to the UL reference signal may include, but is not limited to, a transmission period of the UL reference signal, a time-frequency location of the transmission, information related to decoding of the UL reference signal, and the like. In some embodiments, the UE has established a connection with the macro base station, so the macro base station can learn the configuration information of the UL reference signal of the UE.

In step S2, each micro base station that receives the configuration information receives a UL reference signal from the UE based on the configuration information and measures channel quality information CSI of a channel between the micro base station and the UE. In some embodiments, the micro base station may estimate RSRP or RSRQ of the UL reference signals. In other embodiments, the micro base station may also indicate the channel quality between the micro base station and the UE with other parameters. The scope of the presently disclosed subject matter is not limited in this respect. In some other embodiments, the micro base station may also decode the UL reference signal based on the received configuration information, e.g., decoding information in the configuration information, and use the decoding as a basis for precoding of data communication with the UE thereafter.

In step S3, if the micro base station determines whether the measured CSI satisfies a predetermined condition, and when the predetermined condition is satisfied, for example, RSRP or RSRQ is greater than a predetermined threshold, the measured CSI is transmitted to the macro base station.

In step S4, the macro base station determines how to form a new virtual cell based on the CSI received from the one or more micro base stations. In some embodiments, the macro base station may select one or more small cells from among small cells corresponding to the one or more micro base stations that transmit CSI for forming a new virtual cell. For example, the macro base station may select several small cells with higher CSI for forming a new virtual cell. Alternatively or additionally, the macro base station may select several small cells that are adjacent for forming a virtual cell based on the location of the small cell that sent the CSI. The macro base station may also determine how to form a new virtual cell in accordance with other strategies. For example, the macro base station may combine all small cells corresponding to all micro base stations that transmit CSI into a new virtual cell, or randomly select some small cells from the new virtual cell to form a virtual cell.

In some embodiments, after determining to form a new virtual cell, the macro base station may also configure information about the virtual cell. In one embodiment, the macro base station selects one cell from the small cells forming the new virtual cell as the primary small cell. A primary small cell in a virtual cell may be responsible for scheduling of the virtual cell. For example, the primary small cell may be responsible for scheduling of resources of all small cells of the virtual cell. In some embodiments, the primary small cell may be used to send scheduling information to other small cells in the virtual cell in order to enable coordinated transmissions. For example, the primary small cell may be responsible for transmitting control channels to the UE. The primary small cell may also be responsible for scheduling of data communications with UEs served by the virtual cells, e.g., coordinating one or more of the virtual cells for transmitting data to or receiving data from the UEs. The micro base station serving the primary small cell may be referred to as a Master Transport Point (MTP), a primary radio access node, or a primary micro base station.

In another embodiment, the macro base station may also configure a virtual cell ID (identifier) of the new virtual cell. Alternatively or additionally, the macro base station may also configure the channel transmission mode of the new virtual cell, and/or the configuration of the downlink (UL) reference signal (e.g., period, time-frequency location, codec mode, etc.) and the configuration of the synchronization signal (e.g., period, time-frequency location, codec mode, etc.) of each of the small cells in the virtual cell. The UL reference signal may be a CSI-RS (channel state information-reference signal) in one example.

In step S5, the macro base station transmits an activation message and information on the virtual cell to the micro base station corresponding to each small cell forming the virtual cell. In some embodiments, in response to receiving the activation message, the micro base station may switch to an active state and may thus be used for data communication with the UE. In some embodiments, the information relating to the virtual cell comprises a virtual cell ID and a physical cell ID of each small cell forming the virtual cell. The virtual cell ID may be used to address the entire virtual cell. In this way, each small cell forming a virtual cell can know that it is being used to form the virtual cell and also know the virtual cell ID and the physical cell IDs of other member small cells.

Alternatively or additionally, the information related to the virtual cell may comprise configuration information related to a primary small cell in the virtual cell responsible for scheduling. For example, a physical cell ID of the primary small cell, or other configuration information of the primary small cell. In some other embodiments, the information related to the virtual cell may further include configuration information related to a DL reference signal of each small cell forming the virtual cell or configuration information related to a synchronization signal of each small cell. E.g., the periodicity of the DL reference signals and/or synchronization signals, time-frequency locations, decoding related information, etc. Thereby, the small cell can know how to transmit the DL reference signal and the synchronization signal in the active state. In some further embodiments, information related to the configuration of the DL reference signal and/or synchronization signal of the small cell may also be included in the activation message transmitted to the micro base station.

In step S6, the macro base station transmits information about the virtual cell to the UE. The information transmitted in this step may be the same as or similar to the information related to the virtual cell transmitted to the micro base station in step S5. In some embodiments, a virtual cell may be assigned multiple virtual cell IDs identifying the virtual cell. For example, each UE served by a virtual cell may be assigned a corresponding virtual cell ID. In this case, the macro base station may transmit only the virtual cell ID corresponding to the UE. The macro base station may also transmit a plurality of virtual cell IDs of the virtual cell to each of the small cells in the virtual cell in step S5. In some other cases, a common virtual cell ID may be assigned to multiple users, for example, in a multi-user-multi-input-multi-output (MU-MIMO) application.

In step S7, the UE may also feed back CSI to the primary small cell of the virtual cell. In some embodiments, each micro base station of the virtual cell may broadcast the DL reference signal according to configuration information of the DL reference signal. After the UE receives the configuration information on the DL reference signal of each small cell of the virtual cells from the macro base station in step S6, the DL reference signal may be received based on the configuration information and the channel quality of the DL channel from each micro base station to the UE is measured to obtain the CSI. The UE may report the CSI to the master micro base station of the virtual cell. The CSI obtained here facilitates subsequent data transmission between the micro base station and the UE. For example, the micro base station may decode the CSI and base the decoding on precoding during subsequent data transmission. It should be understood that step S7 is optional.

In step S8, a data communication procedure may be performed between the UE and the virtual cell (i.e., each small cell forming the virtual cell). During this data communication, the primary small cell of the virtual cell may be responsible for scheduling.

Fig. 5 shows a schematic diagram of a communication process 500 in the second scenario described above, i.e. a scenario where the UE is located within the range of a formed virtual cell. The procedure involves the UE under consideration, the macro base station of the macro cell in which the UE is located, and the micro base station corresponding to the small cell in the formed virtual cell. Note that these small cells or micro base stations are all in an active state.

In the process 500, steps S1 to S3 are similar to steps S1 to S3 in the process 400. The difference is that the macro base station sends configuration information about UL reference signals to be transmitted by the UE to the micro base stations of the small cells among the formed virtual cells, the UL reference signals and the measured CSI are received by the micro base stations based on the configuration information, and the measured CSI is reported to the macro base station by the CSI measured by the micro base stations that satisfies a predetermined condition.

In some embodiments, step S3 of process 500 may additionally include transmitting channel state information between each small cell in the virtual cell and each user equipment currently served by the virtual cell to the macro base station. For example, since the micro base station of the primary small cell in the virtual cell may know the CSI between each small cell in the virtual cell and the corresponding user equipment, this CSI may be reported by the primary micro base station. In some embodiments, CSI may be reported only between one or some of the virtual cells and the currently serving one or some user equipments. The scope of the presently disclosed subject matter is not limited in this respect.

Based on the CSI received from the small cell of the virtual cell, including CSI on the UE currently served by the virtual cell, the macro base station may determine whether the UE is served by the virtual cell in step S4. The macro base station may perform this decision based on some policies, e.g. some optimization policies. In some embodiments, the macro base station determines to use this already existing virtual cell for data communication of the UE based on the received CSI. That is, the macro base station schedules the UE into the formed virtual cell. In other embodiments, the macro base station may determine, based on the received CSI, to split the formed virtual cell into two or more new virtual cells and use one of the new virtual cells for data communication for the UE in question. The newly split virtual cell may include one or more small cells in the original virtual cell. In these embodiments, the macro base station may also schedule the UEs served by the previous virtual cell into a new virtual cell after the segmentation, respectively.

Whether the original virtual cell is reserved for serving the new UE or the original virtual cell is split to serve the UE, the virtual cell determined to serve the UE experiences some adjustment (even in the case where the original virtual cell is reserved for serving the UE, the virtual cell is equivalent to experiencing an adjustment due to the addition of the new UE in the virtual cell). Therefore, the macro base station may reconfigure information related to the virtual cell serving the UE. Such information may include one or more of those discussed above with respect to fig. 4. For example, the macro base station may employ a new virtual cell ID. Alternatively or additionally, the macro base station may also configure the channel transmission pattern of the virtual cells, and/or the configuration of downlink (UL) reference signals and the configuration of synchronization signals for each of the small cells in the virtual cell. In the case of reserving the original virtual cell, the macro base station may decide to make the main small cell in the virtual cell continue to be responsible for the scheduling task, or may select another small cell as the main small cell. In the case of splitting the original virtual cell, the macro base station may determine a primary small cell for each virtual cell split.

In step S5, the macro base station transmits information about the virtual cell serving the UE to each of the small cells. This information may include, but is not limited to: a virtual cell ID, a physical cell ID of each small cell forming the virtual cell, configuration information on a primary small cell in charge of scheduling in the virtual cell, and configuration information on a downlink reference signal of each small cell forming the virtual cell.

In step S6, the macro base station also transmits information about the virtual cell to the UE. Step S6 in process 500 is similar to step S6 in process 400.

The UE may also feed back CSI to the primary small cell of the virtual cell in step S7, and may perform a data communication procedure between the UE and the virtual cell (i.e., the small cell forming the virtual cell) in step S8. Steps S7 and S8 in process 500 are similar to steps S7 and S8 in process 400.

Figure 6 shows a schematic diagram of a communication procedure 600 according to the third scenario described above, i.e. in a scenario where the UE is located in an area where both a formed virtual cell and one or more sleeping small cells are present. The procedure involves the UE under consideration, the macro base station of the macro cell in which the UE is located, sleeping micro base stations around the UE, and the micro base stations corresponding to the small cells in the formed virtual cell.

In the process 600, steps S1 to S2 are similar to steps S1 to S2 in the

process

400 or 500. The difference is that the macro base station sends configuration information about UL reference signals to be transmitted by the UE to the micro base stations of the small cells among the formed virtual cells and the sleeping micro base stations around the UE, and the UL reference signals and the measurement CSI are received by these micro base stations based on the configuration information.

In step S3, those of the sleeping micro base stations that measured CSI that satisfies the predetermined condition report the measured CSI to the macro base station. This step is similar to step S3 in process 400.

In step S4, those of the micro base stations of the small cell among the virtual cells that measured CSI that satisfies the predetermined condition report the measured CSI to the macro base station. Similar to step S3 in process 500, the micro base station of the small cell in the formed virtual cell, for example, the main micro base station of the virtual cell, may also transmit channel state information between each small cell in the virtual cell and each user equipment currently served by the virtual cell to the macro base station.

Based on the CSI received from the micro base station of the small cell, the macro base station may determine in step S5 whether to merge the sleeping small cell into the formed virtual cell or whether to serve the UE by the formed virtual cell. The macro base station may perform this decision based on some policies, e.g. some optimization policies. In some embodiments, the macro base station may select one or more small cells from the sleeping small cells that received the CSI and merge the selected small cells into the formed virtual cell. In some embodiments, the macro base station may determine that the already formed virtual cell is not served, but that the selected small cell is used to form a new virtual cell. In some other embodiments, the macro base station may determine that the UE is served by an already formed virtual cell, and the virtual cell does not need to be adjusted. Alternatively, in some embodiments, the virtual cell may be further divided into a plurality of virtual cells, and the divided virtual cell is used for data transmission of the UE.

The virtual cell determined to serve the UE experiences some adjustment regardless of the decision of the macro base station in step S5 (even in the case of serving the UE directly with the original virtual cell, the virtual cell is equivalent to experiencing an adjustment due to the addition of a new UE in the virtual cell). Therefore, the macro base station may reconfigure information related to the virtual cell serving the UE. Such information may include one or more of those discussed above with respect to fig. 4. For example, the macro base station may employ a new virtual cell ID. Alternatively or additionally, the macro base station may also configure the channel transmission pattern of the virtual cells, and/or the configuration of UL reference signals and the configuration of synchronization signals for each of the small cells in the virtual cell. In the case of directly utilizing the original virtual cell, the macro base station may determine to make the main small cell in the virtual cell continue to be responsible for the scheduling task, or may select another small cell as the main small cell. In other cases, the macro base station may determine the primary small cell for the newly formed virtual cell.

In step S6, the macro base station transmits information about the virtual cell serving the UE to each of the small cells. This information may include, but is not limited to: a virtual cell ID, a physical cell ID of each small cell forming the virtual cell, configuration information on a primary small cell in charge of scheduling in the virtual cell, and configuration information on a downlink reference signal of each small cell forming the virtual cell. If the virtual cells serving the UE also include sleeping small cells, the macro base station also sends an activation message to the base stations of these small cells in step S6 in order to switch these sleeping small cells to the active state.

In step S7, the macro base station also transmits information about the virtual cell to the UE. Step S7 in process 600 is similar to step S6 in

process

400 or 400.

The UE may also feed back CSI to the primary small cell among the virtual cells in step S8, and may perform a data communication procedure between the UE and the virtual cells (i.e., the respective small cells forming the virtual cells) in step S9. Steps S8 and S9 in the process 600 are similar to steps S7 and S8 in the

process

400 or 500.

Although fig. 4-6 illustrate one UE, a similar process may be performed for each other UE in the macro cell to communicate using the virtual cell. Although fig. 4-6 illustrate example steps of the process 400-600, in some embodiments, the

process

400, 500, or 600 may include additional steps, fewer steps, different steps, or steps arranged differently than those depicted in fig. 4-6. For example, step S7 in the

processes

400 and 500 and step S8 in the process 600 may be omitted. Additionally or alternatively, two or more steps of the

processes

400, 500, or 600 may be performed in parallel. For example, steps S5 and S6 in

processes

400 and 500 and steps S6 and S7 in process 600 may occur in parallel.

Fig. 7 shows a block diagram of an apparatus 700 for communicating with a virtual cell in a macro base station according to one embodiment of the present disclosure. The coverage area of the macro base station comprises a plurality of small cells. The apparatus 700 may be, for example, or may be included in, a macro base station 110 as shown in fig. 1.

As shown in fig. 7, the apparatus 700 comprises a configuration information transmission unit 710 configured to transmit configuration information related to an uplink reference signal to be transmitted by the UE to a candidate small cell of the plurality of small cells, wherein the configuration information is used by the candidate small cell to receive the uplink reference signal in order to determine channel status information, and the channel status information indicates a channel quality of a channel between the UE and each candidate small cell. The apparatus 700 further comprises a status information receiving unit 720 configured to receive channel status information satisfying a predetermined condition from at least one of the candidate small cells; and a virtual cell determining unit 730 configured to determine a virtual cell for data communication of the UE based on the received channel state information, wherein the virtual cell is formed by one or more of the at least one candidate small cells.

According to some embodiments, the apparatus 700 may further include a candidate small cell determining unit configured to determine, as a candidate small cell, a small cell that is in a sleep state and within a predetermined threshold of distance from the UE.

According to some embodiments, the virtual cell determining unit 730 may comprise a small cell selecting unit configured to select one or more small cells from the at least one candidate small cell based on the channel state information. The virtual cell determining unit 730 may further include a first determining unit configured to determine to use the selected small cell for merging to the formed virtual cell or for forming a new virtual cell when the UE is located within the range of the formed virtual cell; and a second determining unit configured to determine to use the selected small cell for forming a new virtual cell when the UE is not located within the range of the formed virtual cell.

According to some embodiments, the apparatus 700 may further include a primary small cell selection unit configured to select one cell from small cells forming a new virtual cell as a primary small cell when it is determined that the selected small cell is used to form the new virtual cell, wherein the primary small cell is responsible for scheduling of the virtual cell.

According to some embodiments, the apparatus 700 may further comprise a small cell activation unit configured to transmit an activation message to the small cells forming the virtual cell in order to activate the one or more small cells.

According to some embodiments, the UE may be located within the range of the formed virtual cells, and the apparatus 700 may further comprise a candidate small cell determination unit configured to determine small cells of the formed virtual cells as candidate small cells.

According to some embodiments, the virtual cell determining unit 730 may comprise any one of the following: a first determining unit configured to determine to use the formed virtual cell for data communication of the UE based on the channel state information; or a second determining unit configured to determine to use one or more cells of the formed virtual cells in forming a new virtual cell for data communication of the UE based on the channel state information.

According to some embodiments, the above-mentioned channel state information is first channel state information, and the state information receiving unit 720 may be further configured to receive second channel state information from a primary small cell of the formed virtual cell, wherein the second channel state information indicates a channel quality of a channel between a small cell of the formed virtual cell and a UE currently served by the formed virtual cell. In these embodiments, the virtual cell determination unit is further configured to determine the virtual cell for data communication of the UE based on the first channel state information and the second channel state information.

According to some embodiments, the apparatus 700 may further include a virtual cell information transmission unit configured to transmit information related to a virtual cell to the UE and each small cell forming the virtual cell, wherein the information related to the virtual cell includes one or more of: a virtual cell ID of the virtual cell, a physical cell ID of each small cell forming the virtual cell, configuration information on a primary small cell in charge of scheduling in the virtual cell, and configuration information on a downlink reference signal of each small cell forming the virtual cell.

Figure 8 shows a block diagram of an apparatus 800 in a micro base station in a small cell for communicating with a virtual cell according to one embodiment of the present disclosure. The apparatus 800 may be, for example, or may be included in, the micro base station 121-.

As shown in fig. 8, the apparatus 800 includes a configuration information receiving unit 810 configured to receive configuration information related to an uplink reference signal to be transmitted by a UE from a macro base station. The small cell is within the coverage of the macro base station. The apparatus 800 further includes a state information determining unit 820 configured to receive an uplink reference signal from the UE based on the configuration information in order to determine channel state information. The channel state information indicates a channel quality of a channel between the UE and the small cell. The apparatus 800 further comprises a status information transmission unit 830 configured to transmit the channel status information to the macro base station for use by the macro base station in determining a virtual cell for data communication of the UE when the channel status information satisfies a predetermined condition, wherein the virtual cell is formed by at least the small cell.

According to some embodiments, the small cell may be a small cell that is in a sleeping state and within a predetermined threshold of distance from the UE, and the determination by the macro base station to use the small cell for merging into an already formed virtual cell or to use the small cell for forming a new virtual cell.

According to some embodiments, the apparatus 800 may further comprise an activation message receiving unit configured to receive an activation message from the macro base station; and an activation state switching unit configured to switch to an activation state in response to the activation message.

According to some embodiments, the small cell may be a small cell included in the formed virtual cell, and determining, by the macro base station, to use the formed virtual cell for data communication of the UE or to use at least the small cell for forming a new virtual cell for data communication of the UE based on the channel state information.

According to some embodiments, the small cell may be a primary small cell responsible for scheduling among the formed virtual cells. The state information transmitting unit 830 is further configured to transmit second channel state information to the macro base station if the above channel state information is the first channel state information, wherein the second channel state information indicates channel quality of a channel between a small cell among the formed virtual cells and a UE currently served by the formed virtual cells.

According to some embodiments, the apparatus 800 further comprises a virtual cell information receiving unit configured to receive information relating to a virtual cell from the macro base station, wherein the information relating to a virtual cell comprises one or more of: a virtual cell ID of the virtual cell, a physical cell ID of each small cell forming the virtual cell, configuration information on a primary small cell in charge of scheduling in the virtual cell, and configuration information on a downlink reference signal of each small cell forming the virtual cell.

According to some embodiments, the small cell may be determined by the macro base station as the primary small cell among the virtual cells for data communication of the UE. In these embodiments, the apparatus 800 may further include a downlink reference signal transmission unit configured to transmit a downlink reference signal to the UE; and a UE status information receiving unit configured to receive third channel status information from the UE for data communication with the UE, wherein the third channel status information indicates a channel quality of a channel between the UE and each small cell forming the virtual cell.

Fig. 9 shows a block diagram of an apparatus 900 in a UE for communicating with a virtual cell according to one embodiment of the disclosure. The apparatus 900 may be, for example, the UE 140 shown in fig. 1, or may be included therein.

As shown in fig. 9, the apparatus 900 includes a UL reference signal transmission unit 910 configured to transmit an uplink reference signal to the candidate small cell, to cause the candidate small cell to receive the uplink reference signal based on configuration information related to the uplink reference signal received from the macro base station to determine channel state information, and to transmit the channel state information to the macro base station when the channel state information satisfies a predetermined condition. The channel state information indicates state information of a channel between the UE and each candidate small cell.

According to some embodiments, the candidate small cells may comprise at least one of: a small cell in a sleep state and within a predetermined threshold of distance from the UE; and a small cell in the formed virtual cell, wherein the UE is located within a range of the formed virtual cell.

According to some embodiments, the apparatus 900 may further comprise a virtual cell information receiving unit configured to receive information relating to a virtual cell from the macro base station, wherein the information relating to a virtual cell comprises one or more of: a virtual cell ID of the virtual cell, a physical cell ID of each small cell forming the virtual cell, configuration information on a primary small cell in charge of scheduling in the virtual cell, and configuration information on a downlink reference signal of each small cell forming the virtual cell.

According to some embodiments, the aforementioned channel state information is first channel state information, and the apparatus 900 may further include a downlink reference signal receiving unit configured to receive a downlink reference signal from each small cell forming the virtual cell. The apparatus 900 may further include a UE status information determining unit configured to determine second channel status information for data communication of the UE based on the received downlink reference signal, wherein the second status information indicates a channel quality of a channel between the UE and each small cell forming the virtual cell. The apparatus 900 may further include a UE status information transmission unit configured to transmit the second channel status information to a primary small cell in charge of scheduling among the virtual cells.

It can be seen that apparatus 700 of fig. 7 may implement the operations described above with respect to the macro base station in the processes as shown in any one of fig. 3-6, apparatus 800 of fig. 8 may implement the operations described in the processes with respect to the micro base station of the small cell, and apparatus 900 of fig. 9 may implement the processes described in the processes with respect to the UE. Although not further shown, the

apparatus

700, 800 or 900 may comprise further functional units to implement the various embodiments described in connection with fig. 3 to 6.

Embodiments of the present disclosure may also provide a communication system including a macro base station including the apparatus 700 described above with respect to fig. 7. The communication system further comprises micro base stations of at least one small cell, which are within the coverage of the macro base station, and each micro base station comprises the apparatus 800 described above with respect to figure 8. The communication system further includes a UE including the apparatus 900 described above with respect to fig. 9.

It should be noted that the embodiments of the present disclosure can be realized by hardware, software, or a combination of software and hardware. The hardware portion may be implemented using dedicated logic; the software portions may be stored in a memory and executed by a suitable instruction execution system, such as a microprocessor or specially designed hardware. Those skilled in the art will appreciate that the apparatus and methods described above may be implemented using computer executable instructions and/or embodied in processor control code, such code being provided on a carrier medium such as a disk, CD-or DVD-ROM, programmable memory such as read only memory (firmware), or a data carrier such as an optical or electronic signal carrier, for example. The device and its apparatus of the present disclosure may be implemented by hardware circuits such as very large scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above hardware circuits and software, for example, firmware.

It should be noted that although in the above detailed description several units or sub-units of the apparatus are mentioned, this division is only not mandatory. Indeed, the features and functions of two or more of the devices described above may be embodied in one device in accordance with embodiments of the present disclosure. Conversely, the features and functions of one apparatus described above may be further divided into embodiments by a plurality of apparatuses.

Further, while the operations of the disclosed methods are depicted in the drawings in a particular order, this does not require or imply that these operations must be performed in this particular order, or that all of the illustrated operations must be performed, to achieve desirable results. Rather, the steps depicted in the flowcharts may change the order of execution. Additionally or alternatively, certain steps may be omitted, multiple steps may be specified as one step execution, and/or one step may be broken down into multiple step executions.

While the present disclosure has been described with reference to several particular embodiments, it is to be understood that the disclosure is not limited to the particular embodiments disclosed. The disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A communication method implemented in a macro base station, comprising:

transmitting configuration information relating to an uplink reference signal to be transmitted by a user equipment to a candidate small cell of a plurality of small cells, wherein the configuration information is used by the candidate small cell to receive the uplink reference signal in order to determine channel state information, and the channel state information indicates a channel quality of a channel between the user equipment and each candidate small cell;

receiving channel state information satisfying a predetermined condition from at least one of the candidate small cells; and

determining a virtual cell for data communication of the user equipment based on the received channel state information, wherein the virtual cell is formed by one or more small cells of the at least one candidate small cell;

transmitting information related to the virtual cell to the user equipment and each small cell forming the virtual cell, wherein the information related to the virtual cell includes configuration information related to downlink reference signals of each small cell forming the virtual cell,

wherein determining a virtual cell for data communication of the user equipment based on the channel state information comprises:

selecting one or more small cells from the at least one candidate small cell based on the channel state information;

determining to use the selected small cell for merging to an already formed virtual cell or for forming a new virtual cell if the user equipment is located within a range of the already formed virtual cell; and

determining to use the selected small cell for forming a new virtual cell if the user equipment is not within range of the formed virtual cell.

2. The method of claim 1, further comprising:

determining a small cell that is in a sleeping state and within a predetermined threshold of distance from the user equipment as the candidate small cell.

3. The method of claim 1, further comprising:

selecting a cell from the small cells forming a new virtual cell as a primary small cell if it is determined that the selected small cell is to be used for forming the new virtual cell, wherein the primary small cell is responsible for scheduling of the virtual cell and is used for transmitting scheduling information to other small cells in the new virtual cell for realizing coordinated transmission.

4. The method of claim 2, further comprising:

transmitting an activation message to small cells forming the virtual cell in order to activate the one or more sleeping small cells.

5. The method of claim 1, wherein the user equipment is located within a range of a formed virtual cell, the method further comprising:

determining a small cell of the formed virtual cells as a candidate small cell.

6. The method of claim 5, wherein determining a virtual cell for data communication of the user equipment based on the channel state information comprises any one of:

determining to use the formed virtual cell for data communication of the user equipment based on the channel state information; or

Determining, based on the channel state information, to use one or more of the formed virtual cells in forming a new virtual cell for data communication of the user equipment.

7. The method of claim 5, wherein the channel state information is first channel state information, the method further comprising:

receiving second channel state information from a primary small cell of the formed virtual cells, wherein the second channel state information indicates a channel quality of a channel between a small cell of the formed virtual cells and a user equipment currently served by the formed virtual cell, and

determining a virtual cell for data communication of the user equipment based on the first channel state information and the second channel state information.

8. The method of any of claims 1-7, wherein the information related to the virtual cell further comprises one or more of:

a virtual cell identifier, ID, of the virtual cell, a physical cell ID of each small cell forming the virtual cell, and configuration information about a primary small cell in the virtual cell responsible for scheduling.

9. A communication method implemented in a micro base station of a small cell, comprising:

receiving, from a macro base station, configuration information related to an uplink reference signal to be transmitted by a user equipment;

receiving the uplink reference signal from the user equipment based on the configuration information in order to determine channel state information, wherein the channel state information indicates a channel quality of a channel between the user equipment and the small cell; and

transmitting the channel state information to the macro base station for the macro base station to determine a virtual cell for data communication of the user equipment when the channel state information satisfies a predetermined condition, wherein the virtual cell is formed by at least the small cell;

receiving information relating to the virtual cell from the macro base station, wherein the information relating to the virtual cell comprises configuration information relating to downlink reference signals of each small cell forming the virtual cell,

wherein the macro base station determines whether to use the small cell for merging into an already formed virtual cell or to use the small cell for forming a new virtual cell,

wherein the virtual cell for the data communication of the user equipment is determined by the macro base station by:

selecting one or more small cells from at least one of the candidate small cells based on the channel state information;

10. The method of claim 9, wherein the small cell is a small cell that is in a sleeping state and within a predetermined threshold of distance from the user equipment.

11. The method of claim 10, further comprising:

receiving an activation message from the macro base station; and

switching to an active state in response to the activation message.

12. The method of claim 9, wherein the small cell is a small cell included in a formed virtual cell, and determining, by the macro base station, to use the formed virtual cell for data communication of the user equipment or to use at least the small cell for forming a new virtual cell for data communication of the user equipment based on the channel state information.

13. The method of claim 12, wherein the small cell is a primary small cell in charge of scheduling among the formed virtual cells, and the channel state information is first channel state information, the method further comprising:

transmitting second channel state information to the macro base station, wherein the second channel state information indicates channel quality of a channel between a small cell of the formed virtual cells and a user equipment currently served by the formed virtual cell.

14. The method of claim 9, wherein the information related to the virtual cell further comprises one or more of:

15. The method of any of claims 9 to 14, wherein the small cell is determined by the macro base station to be a primary small cell of the virtual cells for data communication of the user equipment, the method further comprising:

transmitting a downlink reference signal to the user equipment; and

receiving third channel state information from the user equipment for the data communication with the user equipment, wherein the third channel state information indicates a channel quality of a channel between the user equipment and each small cell forming the virtual cell.

16. A communication device in a macro base station, comprising:

a configuration information transmission unit configured to transmit configuration information relating to an uplink reference signal to be transmitted by a user equipment to a candidate small cell of a plurality of small cells, wherein the configuration information is used by the candidate small cell to receive the uplink reference signal in order to determine channel state information, and the channel state information indicates a channel quality of a channel between the user equipment and each candidate small cell;

a state information receiving unit configured to receive channel state information satisfying a predetermined condition from at least one of the candidate small cells;

a virtual cell determination unit configured to determine a virtual cell for data communication of the user equipment based on the received channel state information, wherein the virtual cell is formed by one or more small cells of the at least one candidate small cell; and

a virtual cell information transmission unit configured to transmit information related to the virtual cell to the user equipment and each small cell forming the virtual cell, wherein the information related to the virtual cell includes configuration information related to a downlink reference signal of each small cell forming the virtual cell,

wherein the virtual cell determination unit includes:

a small cell selection unit configured to select one or more small cells from the at least one candidate small cell based on the channel state information;

a first determining unit configured to determine to use the selected small cell for merging to an already formed virtual cell or for forming a new virtual cell when the user equipment is located within a range of the already formed virtual cell; and

a second determining unit configured to determine to use the selected small cell for forming a new virtual cell when the user equipment is not within the range of the formed virtual cell.

17. The apparatus of claim 16, further comprising:

a candidate small cell determination unit configured to determine, as the candidate small cell, a small cell that is in a sleeping state and whose distance from the user equipment is within a predetermined threshold.

18. The apparatus of claim 16, further comprising:

a primary small cell selecting unit configured to select one cell from small cells forming a new virtual cell as a primary small cell when it is determined that the selected small cell is used to form the new virtual cell, wherein the primary small cell is responsible for scheduling of the virtual cell and is configured to transmit scheduling information to other small cells in the new virtual cell so as to implement cooperative transmission.

19. The apparatus of claim 17, further comprising:

a small cell activation unit configured to transmit an activation message to small cells forming the virtual cell in order to activate the one or more sleeping small cells.

20. The apparatus of claim 16, wherein the user equipment is located within a range of a formed virtual cell, the apparatus further comprising:

a candidate small cell determination unit configured to determine a small cell of the formed virtual cells as a candidate small cell.

21. The apparatus according to claim 20, wherein the virtual cell determining unit comprises any one of:

a first determining unit configured to determine to use the formed virtual cell for data communication of the user equipment based on the channel state information; or

A second determining unit configured to determine to use one or more cells of the formed virtual cells in forming a new virtual cell for data communication of the user equipment based on the channel state information.

22. The apparatus according to claim 20, wherein the channel state information is first channel state information, and the state information receiving unit is further configured to receive second channel state information from a primary small cell of the formed virtual cells, wherein the second channel state information indicates a channel quality of a channel between a small cell of the formed virtual cells and a user equipment currently served by the formed virtual cell, and

wherein the virtual cell determination unit is further configured to determine a virtual cell for data communication of the user equipment based on the first channel state information and the second channel state information.

23. The apparatus according to any of claims 16 to 22, wherein the information relating to the virtual cell further comprises one or more of: a virtual cell identifier, ID, of the virtual cell, a physical cell ID of each small cell forming the virtual cell, and configuration information about a primary small cell in the virtual cell responsible for scheduling.

24. A communication device in a micro base station of a small cell, comprising:

a configuration information receiving unit configured to receive configuration information about an uplink reference signal to be transmitted by a user equipment from a macro base station;

a state information determination unit configured to receive the uplink reference signal from the user equipment based on the configuration information to determine channel state information, wherein the channel state information indicates a channel quality of a channel between the user equipment and the small cell;

a state information transmission unit configured to transmit the channel state information to the macro base station for the macro base station to use to determine a virtual cell for data communication of the user equipment when the channel state information satisfies a predetermined condition, wherein the virtual cell is formed by at least the small cell; and

a virtual cell information receiving unit configured to receive information on the virtual cell from the macro base station, wherein the information on the virtual cell includes configuration information on a downlink reference signal of each small cell forming the virtual cell,

25. The apparatus of claim 24, wherein the small cell is a small cell that is in a sleeping state and within a predetermined threshold of distance from the user equipment.

26. The apparatus of claim 25, further comprising:

an activation message receiving unit configured to receive an activation message from the macro base station; and

an activation state switching unit configured to switch to an activation state in response to the activation message.

27. The apparatus of claim 24, wherein the small cell is a small cell included in a formed virtual cell, and determining, by the macro base station, to use the formed virtual cell for data communication of the user equipment or to use at least the small cell for forming a new virtual cell for data communication of the user equipment based on the channel state information.

28. The apparatus of claim 27, wherein the small cell is a primary small cell in charge of scheduling in the formed virtual cell, and the channel state information is first channel state information, and

wherein the state information transmission unit is further configured to transmit second channel state information to the macro base station, wherein the second channel state information indicates a channel quality of a channel between a small cell of the formed virtual cells and a user equipment currently served by the formed virtual cell.

29. The apparatus of claim 24, wherein the information related to the virtual cell further comprises one or more of: a virtual cell identifier, ID, of the virtual cell, a physical cell ID of each small cell forming the virtual cell, and configuration information about a primary small cell in the virtual cell responsible for scheduling.

30. The apparatus of any of claims 24 to 29, wherein the small cell is determined by the macro base station to be a primary small cell of the virtual cells for data communication of the user equipment, the apparatus further comprising:

a downlink reference signal transmission unit configured to transmit a downlink reference signal to the user equipment; and

a user equipment state information receiving unit configured to receive third channel state information from the user equipment for the data communication with the user equipment, wherein the third channel state information indicates a channel quality of a channel between the user equipment and each small cell forming the virtual cell.

31. A communication system, comprising:

a macro base station comprising an apparatus according to any of claims 16 to 23;

a micro base station of at least one small cell, each micro base station of a small cell comprising an apparatus according to claims 24 to 30.