Method and apparatus for transmitting reference signals from multiple cells in a dormant mode

Abstract

Various embodiments of the present disclosure relate to a method and apparatus for transmitting reference signals from a plurality of cells in a dormant mode. A method includes receiving at least one reference signal from a first cell in a less active state and receiving at least one reference signal from a second cell in a less active state in the same or different subframes of a subframe group, wherein the at least one reference signal from the first base station is associated with resource elements of the subframe group, which are different from the resource elements associated with the at least one reference signal from the second cell.

Description

[0001] This application is a divisional application of the invention patent application with the application date of January 18, 2013, application number 201380070620.6, and invention title "Method and apparatus for transmitting reference signals from multiple cells in a sleep mode". Technical Field

[0002] The present invention relates to a method and an apparatus, and more specifically, but not exclusively, to a method and an apparatus in a cell or a network node with a relatively low active mode. Background Art

[0003] A communication system can be regarded as a facility that enables a communication session between two or more nodes, such as fixed or mobile devices, machine type terminals, access nodes such as base stations, servers, etc. Communication systems and compatible communication entities generally operate according to a given standard or specification, which stipulates what various entities associated with the system are allowed to do and how to implement them. For example, standards, specifications, and related protocols can define how devices communicate, how various aspects of communication are implemented, and how devices for the system are configured.

[0004] A user can access the communication system through a suitable communication device. The user's communication device is usually referred to as a user equipment (UE) or a terminal. Appropriate signal reception and transmission arrangements are provided for the communication device to enable it to communicate with other parties. A typical device, such as a user equipment, is used to enable communication to receive and transmit, such as voice and content data.

[0005] Communication can be carried on a wireless carrier. Examples of wireless systems include public land mobile networks (PLMNs) such as cellular networks, satellite-based communication systems, and different wireless local area networks, such as wireless local area networks (WLANs). In a wireless system, a communication device provides a transceiver station that can communicate with another communication device, such as a base station of an access network and / or another user equipment. The two communication directions between a base station and a user communication device have been conventionally referred to as the downlink and the uplink. The downlink (DL) can be understood as the direction from the base station to the communication device, and the uplink direction (UL) can be understood as the direction from the communication device to the base station. Summary of the Invention

[0006] According to one aspect, the present invention provides a method, including: receiving at least one reference signal from a first cell in a relatively less active state and receiving at least one reference signal from a second cell in a relatively less active state in the same or different subframes of a subframe group. Wherein the at least one reference signal from the first base station is associated with resource elements of the subframe group, which are different from the resource elements associated with the at least one reference signal from the second cell.

[0007] Each cell has an identifier associated therewith, and the position of at least one reference signal from respective cells depends on the cell identifier.

[0008] According to one aspect, this aspect provides a method, including: receiving at least one reference signal from a first cell in a less active state, the position of the reference signal depending on the cell identifier.

[0009] According to one aspect, the present invention provides a method, including: causing at least one reference signal to be transmitted from a first cell in a less active state, the position of the reference signal depending on the cell identifier.

[0010] The at least one reference signal of the first cell can be provided in one subframe of a subframe group and on resource elements different from those of the subframe used by a second cell.

[0011] It is worth mentioning that any one or more of the following features can be combined with any one or more of the above aspects.

[0012] The position depends on a modulo operation performed according to the cell identifier.

[0013] The modulo operation can depend on a plurality of available positions in the subframe group for respective at least one reference signal of different cells.

[0014] The at least one reference signal can include a reference signal provided by two adjacent symbols of the same subframe.

[0015] Each of the at least one reference signal can include a synchronization signal.

[0016] The synchronization signal can include a primary synchronization signal and / or a secondary synchronization signal.

[0017] The at least one reference signal can include a reference signal provided using p resource elements of at least one symbol, each symbol having q resource elements, where p is less than q.

[0018] The at least one reference signal can be provided using a plurality of resource elements of at least two different symbols, at least two of the resource elements being located on different subcarriers.

[0019] The symbol can include an orthogonal frequency division multiplexing symbol.

[0020] Each of the at least one reference signal can include a common reference signal.

[0021] The group can include a plurality of consecutive subframes.

[0022] The frame group is repeated x times to provide a burst, where x is an integer.

[0023] According to another aspect, the present invention provides a reference signal transmitted from a first cell, where the first cell is in a less active state, and the position of the reference signal in the subframe depends on the cell identifier.

[0024] According to another aspect, the present invention provides an apparatus including: means for receiving at least one reference signal from a first cell in a less active state and at least one reference signal from a second cell in a less active state in the same or different subframes of a subframe group, where the at least one reference signal from the first base station is associated with resource elements of the subframe group, which are different from the resource elements associated with the at least one reference signal from the second cell.

[0025] Each cell may have an identifier associated therewith, and the position of the at least one reference signal from each respective cell depends on the cell identifier.

[0026] The apparatus may be provided in a user equipment.

[0027] According to one aspect, the present invention provides an apparatus including: means for receiving at least one reference signal from a first cell in a less active state, where the position of the reference signal depends on the cell identifier.

[0028] The apparatus may be provided in a user equipment.

[0029] According to one aspect, the present invention provides an apparatus including: means for causing at least one reference signal to be transmitted from a first cell, where the first cell is in a less active state, and the position of the reference signal depends on the identifier of the cell.

[0030] The at least one reference signal of the first cell may be provided in a subframe of a subframe group and on resource elements different from those of the subframe used by the second cell.

[0031] The apparatus may be provided in a cell or a base station.

[0032] It is worth mentioning that any one or more of the following features can be combined and used with any one or more of the above aspects.

[0033] The position depends on a modulo operation performed according to the cell identifier.

[0034] The modulo operation may depend on a plurality of available positions in the subframe group for different cells to use for their respective at least one reference signals.

[0035] The at least one reference signal may include a reference signal provided by two adjacent symbols of the same subframe.

[0036] Each of the at least one reference signal may include a synchronization signal.

[0037] The synchronization signal may include a primary synchronization signal and / or a secondary synchronization signal.

[0038] The at least one reference signal may include a reference signal provided using p resource elements of at least one symbol, each symbol having q resource elements, where p is less than q.

[0039] The at least one reference signal may be provided using multiple resource elements of at least two different symbols, at least two of the resource elements being located on different subcarriers.

[0040] The symbol may include an orthogonal frequency division multiplexing symbol.

[0041] Each of the at least one reference signal may include a common reference signal.

[0042] The set may include a plurality of consecutive subframes.

[0043] The set of frames is repeated x times to provide a burst, where x is an integer.

[0044] According to another aspect, the present invention provides an apparatus including at least one processor and at least one memory, the memory including computer code for one or more programs, the computer code being configured by the at least one processor to cause the apparatus to at least: receive at least one reference signal from a first cell in a same or different subframe of a set of subframes, the first cell being in a less active state, and receive at least one reference signal from a second cell in a same or different subframe of the set of subframes, the second cell being in a less active state. Wherein the at least one reference signal from the first base station is associated with resource elements of the set of subframes, which are different from the resource elements associated with the at least one reference signal from the second cell.

[0045] Each cell may have an identifier associated therewith, and the position of the at least one reference signal from each respective cell depends on the cell identifier.

[0046] The apparatus may be provided in a user equipment.

[0047] According to another aspect, the present invention provides an apparatus including at least one processor and at least one memory, the memory including computer code for one or more programs, the computer code being configured by the at least one processor to cause the apparatus to at least: receive at least one reference signal from a first cell in a less active state, the position of the reference signal depending on the cell identifier.

[0048] The apparatus may be provided in a user equipment.

[0049] According to another aspect, the present invention provides an apparatus comprising at least one processor and at least one memory, the memory comprising computer code for one or more programs, the computer code being configured by the at least one processor to cause the apparatus to at least: cause at least one reference signal to be transmitted from a first cell, the first cell being in a less active state, the position of the reference signal depending on the cell identifier.

[0050] The at least one reference signal of the first cell can be provided in a subframe of a group of subframes and on resource elements different from those used by a second cell.

[0051] The apparatus can be provided in a cell or a base station.

[0052] It is worth mentioning that any one or more of the following features can be used in combination with any one or more of the above aspects.

[0053] The position depends on a modulo operation performed according to the cell identifier.

[0054] The modulo operation can depend on multiple available positions in the group of subframes for respective at least one reference signal of different cells.

[0055] The at least one reference signal can include a reference signal provided by two adjacent symbols of the same subframe.

[0056] Each of the at least one reference signal can include a synchronization signal.

[0057] The synchronization signal can include a primary synchronization signal and / or a secondary synchronization signal.

[0058] The at least one reference signal can include a reference signal provided using p resource elements of at least one symbol, each symbol having q resource elements, where p is less than q.

[0059] The at least one reference signal can be provided using multiple resource elements of at least two different symbols, at least two of the resource elements being located on different subcarriers.

[0060] The symbol can include an orthogonal frequency division multiplexing symbol.

[0061] Each of the at least one reference signal can include a common reference signal.

[0062] The group can include multiple consecutive subframes.

[0063] The group of frames is repeated x times to provide a burst, where x is an integer.

[0064] Any of the above methods can be performed by an apparatus. The apparatus can be provided in a user equipment, a cell device or a base station device.

[0065] The present invention also provides a computer program comprising program code means adapted to perform the method. The computer program may be stored and / or embodied in a carrier medium.

[0066] It is noted that any feature of any aspect may be used in combination with other features of any other aspect. Brief Description of the Drawings

[0067] By way of example only, in conjunction with the following examples and drawings, the embodiments will be described in detail below:

[0068] Figure 1 Shows a schematic diagram of a communication system including a base station and a plurality of communication devices;

[0069] Figure 2 Shows a schematic diagram of a mobile communication device according to some embodiments;

[0070] Figure 3 Shows a schematic diagram of a control device according to some embodiments;

[0071] Figure 4 Schematically shows the active state and the sleep state of a base station;

[0072] Figure 5 Shows a physical resource block that may be received by a user equipment;

[0073] Figure 6 Shows a method of an embodiment;

[0074] Figure 7 Schematically shows a device of a cell; and

[0075] Figure 8 Schematically shows a device of a user equipment. Detailed Description of the Embodiments

[0076] With reference to a wireless or mobile communication system serving mobile communication devices, some exemplary embodiments will be described below. Before detailing the exemplary embodiments, reference is made to Figure 1-3 , and certain general principles of wireless communication systems and mobile communication devices are briefly explained to assist in understanding the technology underlying the described examples.

[0077] In a wireless communication system, wireless access is provided to mobile communication devices or user equipment (UE) 102, 103, 105 via at least one base station or similar wireless transmission and / or reception node or point. Figure 1The example shows two overlapping access systems or wireless service areas of cellular systems 100, 110 and three smaller radio service areas 115, 117 and 119 provided by base stations 106, 107, 116, 118 and 120. Each mobile communication device and station may have one or more radio channels open at the same time and can transmit signals to and / or receive signals from multiple sources. It is noted that Figure 1 the boundaries or edges of the wireless service areas shown are for illustrative purposes only. It should also be understood that the size and shape of the radio service areas may vary significantly from Figure 1 their shape. A base station site may serve one or more cells. A single base station can provide multiple sectors simultaneously, for example, three radio sectors, each providing a cell or a sub-region of a cell. All sectors within a cell can be served by the same base station.

[0078] Base stations are typically controlled by at least one suitable control device to enable them to operate and manage the mobile communication devices communicating with the base station. In Figure 1 the example, control devices 108 and 109 are shown controlling their respective macro-level base stations 106 and 107. The control devices of the base stations can be interconnected with other control entities. The control device typically has a storage capacity and at least one data processor. The control device and functions can be distributed among multiple control units. In some systems, the control device can also be provided additionally or optionally in a radio network controller.

[0079] In Figure 1 the example, stations 106 and 107 are shown connected to a wider communication network 113 via gateway 112. Further gateway functionality can be provided to connect to another network.

[0080] The smaller stations 116, 118 and 120 can also be connected to network 113, such as by separate gateway functionality and / or via the controller of the macro-level station. In the example, stations 116 and 118 are connected via gateway 111, while station 120 is connected via controller device 108. In some embodiments, the smaller stations are not provided.

[0081] Referring to Figure 2 a partial cross-sectional view of communication device 200 is schematically shown, a possible mobile communication device will be described in more detail. This may be Figure 1Any one of the communication devices 102, 103, and 105. Such a communication device is commonly referred to as a user equipment (UE) or a terminal. A suitable mobile communication device can be provided by any device capable of sending and receiving wireless signals. Non-limiting examples include a mobile station (MS), such as a mobile phone or what is referred to as a "smartphone", a computer with a wireless interface card or other wireless interface device, a personal digital assistant (PDA) with wireless communication capabilities, or any combination of these or the like. The mobile communication device can provide, for example, communication for carrying communication data, such as voice, email, text messages, multimedia, etc. A multitude of services can be provided to the user through the user's communication device. Non-limiting examples of these services include two-way or multi-way telephone, data communication or multimedia services, or just access to a data communication network system, such as the Internet. Broadcast or multicast data can also be provided to the user. Non-limiting examples of this content include downloads, television and radio programs, videos, advertisements, various alerts, and other information.

[0082] The mobile device 200 can receive signals over the air interface 207 through a suitable means for reception and can transmit signals through a suitable means for transmitting radio signals. Figure 2 In, the transceiver means is schematically shown by block 206. For example, the transceiver means 206 can be provided through radio components and associated antenna arrangements. The antenna arrangement can be located inside or outside the mobile device.

[0083] The wireless communication device can have a multiple-input multiple-output (MIMO) antenna system. Such as a well-known MIMO arrangement. The MIMO system uses multiple antennas at the transmitter and receiver and uses advanced digital signal processing to improve link quality and capacity. Although Figure 1 and 2 is not shown in, multiple antennas can be provided, for example, at the base station and the mobile station, and Figure 2 the transceiver means 206 in can provide multiple antenna ports. With more antenna elements, more data can be received and / or transmitted. A station can include a multi-antenna array. The signaling and silent modes can be associated with the number of TX antennas or the number of MIMO arrangement ports.

[0084] The mobile device 200 typically has at least one data processing entity 201, at least one memory 202 and other possible components 203 for assisting in the implementation of tasks in software and hardware, which tasks are designed to implement, including access control to access systems and other communication devices and communication with access systems and other communication devices. Data processing, storage and other related control means may be provided on a suitable circuit board and / or in a chipset. This feature is denoted by reference 204. The user can control the operation of the mobile device through a suitable user interface, such as a keyboard 205, voice commands, a touch-sensitive screen or pad, a combination of these or the like. A display 208, a speaker and a microphone may also be provided. In addition, the mobile communication device may include appropriate connectors (wired or wireless) to connect to other devices and / or to connect external accessories, such as a hands-free device.

[0085] Figure 3 An example of a control device for a communication system is shown, for example, a station coupled to an access system and / or a station for controlling an access system, such as a base station. In some embodiments, the base station includes a separate control device. In other embodiments, the control device may be another network element, such as a radio network controller. In some embodiments, each base station has such a control device, and the control device is provided in the radio network controller. The control device 109 may be arranged in the service area of the system to provide control of communications. The control device 109 includes at least one memory 301, at least one data processing unit 302, 303 and an input / output interface 304. Through this interface, the control device can be coupled to the receiver and transmitter of the base station. The control device 109 may be configured to execute appropriate software code to provide this control function.

[0086] The communication devices 102, 103, 105 may access the communication system based on various access technologies, such as code division multiple access (CDMA), or wideband CDMA (WCDMA). Other examples include time division multiple access (TDMA), frequency division multiple access (FDMA) and its various schemes, such as interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA), etc.

[0087] An example of a wireless communication system is an architecture standardized by the 3rd Generation Partnership Project (3GPP). New 3GPP-based developments are generally referred to as the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology. Different development stages of the 3GPP LTE regulations are referred to as releases. The most recent development of LTE is often referred to as LTE-Advanced (LTE-A). LTE employs a mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The base stations of such a system are called evolved or enhanced Node Bs (eNBs) and can provide E-UTRAN features such as the user plane Radio Link Control / Medium Access Control / Physical layer protocol (RLC / MAC / PHY) and the control plane Radio Resource Control (RRC) protocol towards the user equipment terminals. Other examples of radio access systems include those provided by base stations based on technologies such as Wireless Local Area Network (WLAN) and / or WiMAX (Worldwide Interoperability for Microwave Access).

[0088] As part of 3GPP Release 12, work items on NCT (New Carrier Type) were proposed and agreed upon. The carrier can be used in such a way as to achieve one or more of the following objectives: network energy saving; overhead reduction; enhanced support for deployment, which includes one or more smaller cells that at least partially overlap with a larger cell. The deployment of one or more smaller cells overlapping with a larger cell (e.g., macro cell) is sometimes also referred to as a HetNet deployment.

[0089] For network energy saving, when there is no data to transmit, the base station can be controlled to allow completely blank subframes. This means that the transmitter can be at least partially turned off.

[0090] In cases where DM RS (Demodulation Reference Signal) can be used, overhead reduction can be achieved by reducing the overhead of CRS (Common Reference Signal). Overhead reduction is particularly beneficial for, for example, beamforming MIMO (Multiple-Input Multiple-Output) with four or more antennas. In cases such as the HetNet scenario described above, interference from common signals can be reduced.

[0091] Some embodiments may provide base stations that support dual sleep / active states. This may imply the behavior of DTX (Discontinuous Transmission) type base stations, having, for example, relatively long DTX cycles. The UE can execute procedures to take into account the state of the base station. In some embodiments, the CRS may be reduced in the active state.

[0092] Some embodiments may allow base stations to save energy using sleep operations. Signals can be provided to allow neighbor cell discovery and RRM (Radio Resource Management) measurements.

[0093] In some embodiments, energy efficiency can be achieved by scheduling transmissions in as few DL subframes as possible. In this way, the remainder of the subframe can be kept empty ("blank") and the transmitter of the eNodeB can be turned off in these subframes to save energy.

[0094] Some embodiments relate to the use of eNodeB (eNB) sleep characteristics of a carrier, for example, in the context of small cells. For example, a small cell may be a microcell, a HetNet cell, or a similar cell.

[0095] However, even if a cell / carrier does not carry any traffic, common signals and channels may still be required, such as one or more PDCCH (Physical Downlink Control Channel), PHICH (Physical Hybrid ARQ (Automatic Repeat reQuest) Indicator Channel), PCFICH (Physical Control Format Indicator Channel), PSS and SSS (Primary Synchronization Signal / Secondary Synchronization Signal), PCH (Paging Channel), PBCH (Physical Broadcast Channel), SIB (System Information Block), CRS (Common (Cell-Specific) Reference Signal), and CSI-RS (Channel State Information Reference Signal), for example, to support mobility.

[0096] In some embodiments, to achieve energy savings, when not needed, it is desirable to avoid the need to transmit common (cell-specific) signals. A duty cycle is provided to replace the transmission of common channels and signals such as CRS, PDCCH, PHICH, PCFICH in each subframe. For example, the duty cycle can be 5 ms. However, in other embodiments, different duty cycles can be used. Different duty cycles can be greater than or less than 5 ms. When the duty cycle is 5 ms, this will result in the common signal only appearing in every fifth frame. At low network loads, this will allow the eNodeB, for example, to gradually reduce at least some transmitter functions (such as power amplifiers) to save energy and reduce interference.

[0097] Optionally, eNodeB sleep / DTX (Discontinuous Transmission) - type operation can be provided. In this alternative, the network will suspend the transmission of all common signals and channels for a period longer than the said 5 ms.

[0098] It can be understood that in some embodiments, the eNodeB or base station sleep operation can be applied to a carrier with all common signals, or a carrier with reduced common signals. A carrier with all common signals may be a so-called traditional carrier. A carrier with reduced common signals may be a so-called new carrier type.

[0099] Refer to Figure 4 , which illustrates the operation of a base station with sleep and active states. In particular, in Figure 4In the arrangement, the base station has a first sleep state 400, followed by an active state 402, followed by another sleep state 404. In the first sleep state 400, there is a first DTX off period 406, followed by a DTX on period 408, and then a second DTX off period 410. When the base station is in the DTX off period, the base station generally does not transmit. When the base station is in the DTX on state, some signals are transmitted, such as allowing the exploration of adjacent cells and / or for example allowing RRM measurements required for cell selection.

[0100] In the active state 402, state 412 is that common signals are transmitted during this active state. In other words, the base station operates normally and sends signals to the user equipment. In the second sleep state 404, there is a first DTX off state 414, followed by a DTX on state 416, and then a DTX off state 418. In some embodiments, the DTX on state can last for a relatively large number of subframes, and can for example last for more than 10 subframes.

[0101] In some embodiments, it is advantageous to align the DTX on periods of adjacent cells from the perspective of the UE and / or the network. For the UE, aligning and synchronizing the DTX on periods of two or more cells allows two or more cells to be discovered in a shorter time. This can reduce the energy consumption of the UE. This can alternatively or additionally affect the data throughput, because when performing measurements on neighboring cells, the UE may not be able to send / receive data. Generally, a so-called "measurement gap" is configured.

[0102] From the perspective of the network, enabling the UE to measure as many neighboring cells as possible simultaneously can reduce data transmission interruptions due to measurement gaps. In other words, the number and / or duration of measurement gaps can be reduced.

[0103] In the DTX on period of the sleep base station state, some embodiments can provide signals and / or configuration options for the discovery or reference signals and / or the multiplexing of signals of these different cells or transmission points.

[0104] In some embodiments, the transmission of synchronization and / or reference signals is implemented so as to enable fast and / or efficient cell search.

[0105] In some embodiments, the DTX discovery signal (DOD) can be defined as, for example, a reference signal transmitted within a given period. The DOD can be defined as a signal transmitted when the base station is in a dormant state, but some basic signals are transmitted. These basic signals can be reference signals. The reference signal can be a combination of PSS / SSS and CRS. The given period can be a subframe. In other embodiments, the given period can be longer than a subframe. The DOD signal can be provided in a single subframe, or can be provided by a burst that is transmitted over two or more subframes. In some embodiments, the DOD signal of a given base station can be repeated in multiple subframes. In some embodiments, the subframes transmitting the DOD signal are non-consecutive.

[0106] In some embodiments, the components of the DOD signal can be based on signals that have already appeared in the existing LTE standard, namely PSS / SSS and CRS. To provide orthogonality for the DOD signal, the time and / or frequency position (i.e., resource element) of PSS / SSS and CRS in a subframe can be deterministically varied between cells.

[0107] The DOD configuration (i.e., the combination of PSS / SSS and CRS positions) may be obtained, for example, based on the physical cell ID and modulo operation. An example will be given later.

[0108] Currently, 504 physical cell IDs (PCIs) are defined. Of course, this may be different under different standards and different versions of this standard. As described below, in certain embodiments, the indexed DOD signal has 20 unique (orthogonal) positions, such as 0…19. The indexing of the position of the DOD signal is given by the following formula:

[0109] Index of DOD = PCI modulo 20

[0110] It is worth mentioning that the index can be generalized to one of x different positions, where x is the number of unique positions in the duty cycle. x is an integer. Thus, the index can be generalized as Index of DOD = PCI modulo X.

[0111] Optionally or additionally, the position can be signaled. When the corresponding measurement object is configured (in a similar way that different measurement modes for different cell ID groups can be configured in Rel-8), the position can be signaled using, for example, a dedicated RRC (Radio Resource Control) signal. When the network configures the UE to perform measurements on a carrier at a given frequency, the network can also provide information related to, for example, the reference signal configuration. The reference signal information will indicate in which subframe or subframes, at which frequency or frequencies, the UE should search for the reference signal from a base station or cell in an inactive mode.

[0112] In some embodiments, DOD signals of different cells may be sent in different predetermined subframes.

[0113] The DOD signal for a given cell may be sent in a burst of, for example, 2 - 10 subframes. It is worth mentioning that in certain embodiments, the number of such subframes may be one or, in some cases, may exceed 10. The subframes may be consecutive or non - consecutive subframes or a mixture of consecutive and non - consecutive. The DOD signal may be regarded as an overall burst, consisting of CRS / PSS / SSS repeated Y times in every N subframes. In alternative embodiments, the DOD signal may optionally be considered as a reference signal or a signal sent by a given cell in one subframe.

[0114] In some embodiments, the duty cycle of the DOD signal in the burst may be 5 milliseconds, which means that the duty cycle is aligned with that of the so - called new carrier type. However, in other embodiments, the duty cycle may be greater than or less than 5 ms. The DOD signal may repeat every 5 ms. The burst is optionally or additionally defined by the number of subframes.

[0115] In some embodiments, there is information exchange between eNBs. This information exchange is used to ensure that eNBs within each other's range coordinate their respective configurations. This information exchange may be through wired and / or wireless interfaces. An example of an interface is the X2 interface. Optionally or additionally, information may be provided through wireless exchange, where eNBs communicate through the air interface. The information exchange may be based on the implementation of a Network Listening Mode (NLM), where a new eNB listens to the configurations of current neighbors and adapts to these configurations to minimize the impact on their respective configurations.

[0116] Optionally or additionally, a controller may control the base stations to ensure that their respective configurations are coordinated. The signal may be provided to one or more base stations by the controller. The controller may be an entity such as a Radio Network Controller or the like.

[0117] In this way, each base station knows when it should send its DOD, and this will be at a different time from another base station. In some embodiments, multiple different base stations will use the same PRB and send their DODs in the same subframe, but use, for example, different symbols and / or subcarriers.

[0118] In LTE, the PSS / SSS for a given base station may be transmitted twice in each radio frame, in subframe #0 and #5. This may be used with the so - called new carrier type. Some embodiments may follow this pattern. However, other embodiments may use different patterns.

[0119] In one embodiment of the DOD signal, taking FDD (Frequency Division Duplexing) and normal CP (Cyclic Prefix) as examples, the following orthogonal time positions in the same subframe are available in some embodiments:

[0120] OFDMA symbol pairs {1, 2}, {2, 3}, {5, 6}, {8, 9}, {9, 10}, {12, 13}

[0121] These symbol pairs are used to transmit the PSS and SSS signals. It is worth mentioning that in other embodiments, one or more different symbol pairs are available. It should be realized that optionally, the PSS / SSS may be sent by non - adjacent symbols.

[0122] However, some pairs are mutually exclusive, and it can be easily found that there are four unique pairs (e.g., {1, 2}, {5, 6}, {8, 9}, {12, 13}). With a duty cycle of 5 subframes, a total of 4×5 = 20 PSS / SSS completely orthogonal sequences can be multiplexed for one radio frame. In other words, up to 20 different base stations can be supported. On the other hand, each of these 5 subframes can support four different base stations in the dormant DTX - on mode. Then, this pattern can be repeated. The multiplexing capacity can be further obtained by using different frequency resources (i.e., PRB - Physical Resource Blocks) for PSS / SSS transmission. In other words, if additional physical resource blocks are used for PSS / SSS transmission, each subframe of each PRB can support four different base stations.

[0123] The CRS component of the DOD signal can be for the purpose of frequency and / or time tracking. This component can be a single CRS port transmitted with a 5 - ms duty cycle. Orthogonality can be obtained by one or more of the following methods:

[0124] Different CRS frequency shifts can be utilized: for example, LTE Rel - 8 supports six different sub - carrier positions for the CRS.

[0125] Different CRS ports can be utilized: RES (Resource Elements) corresponding to CRS port 0 or 1 can be used. However, if all 6 frequency shifts are used, this may not provide further orthogonality.

[0126] Changing the CRS position in time: Similar to having PSS / SSS, assuming the duty cycle of the CRS is 5 subframes, interleave the transmission of CRSs corresponding to different cells' DODs. Combining with CRS frequency shift, this provides a total of 6 x 5 = 30 unique time-frequency resources for the DOD signal. Each subframe can support 6 different base stations. A duty cycle of 5 subframes would mean that 30 base stations can be supported. Of course, in some embodiments, only 4 base stations need to be supported in one subframe because the PSS / SSS requirements mean that only four base stations can be supported in one subframe.

[0127] It can be understood that in some embodiments, the PSS / SSS and CRS for a given base station will be provided in the same subframe.

[0128] Reference Figure 5 illustrates the multiplexing principle according to one embodiment. Figure 5 The illustration shows a signal that can be received by a UE. Here only one PRB pair is shown. For example, in 3GPP, one PRB pair has a duration of 1 ms and has 12 subcarriers. A PRB includes two 0.5-ms time slots, and technically, one PRB is 12 subcarriers × 0.5 ms. The physical resource block pair consists of 14 symbols. Each symbol consists of 12 resource elements, and each resource element of a symbol is associated with a different subcarrier. As described above, four fully orthogonal time-frequency resources can be provided for the DOD signal composed of PSS / SSS and CRS. Additionally, adding, for example, a 5-ms subframe-level duty cycle on top further increases the capacity. In Figure 5 the arrangement, four symbol pairs provide the corresponding PSS / SSS signals labeled SS1, SS2, SS3, and SS4. Each symbol pair is provided to each of the 12 subcarriers. Each symbol pair provides the PSS and SSS signals for a respective different base station. The CRS signal is provided in symbols 0, 4, 7, and 9. Each of these symbols provides a partial CRS signal for up to 6 different base stations. Some different subcarriers in the symbols are used for the CRS signals from different base stations. For example, subcarriers 0 and 6 in symbols 0 and 7, and subcarriers 3 and 9 in symbols 4 and 11, provide the CRS signal for the first base station. Subcarriers 1 and 7 in symbols 0 and 7, and subcarriers 4 and 10 in symbols 4 and 11, provide the CRS signal for the second base station, and so on.

[0129] In some embodiments, as previously described in combination with PSS / SSS and CRS, some embodiments may have one or more of the following advantages: multiple fully orthogonal discovery signals can be constructed (up to 20, excluding the PSS / SSS frequency offset in some embodiments);

[0130] use of existing implementations;

[0131] Universal applicability of at least partially Rel-11 type with NCT design; and

[0132] Through coordination between eNBs, it is possible to achieve coordinated transmission muting in the affected PRB pairs in order to more accurately estimate the path loss to adjacent cells and create a scenario with lower intra-cell interference.

[0133] This PSS / SSS sequence defines the physical cell ID (one of 504 options). In addition, modular arithmetic binds the physical cell ID to the position of the DOD signal. In this way, the UE will know which reference signals are associated with which base stations or cells. It is worth mentioning that the CRS position can be bound to the position associated with this PSS / SSS sequence.

[0134] Reference Figure 6 , which illustrates a method of an embodiment. In step S1, the cell enters a less active or dormant mode. This can be controlled by the cell itself and / or by a controller, such as a radio network controller.

[0135] In step S2, the cell determines the timing of the reference signal. In particular, the cell determines when and on which resources to send the reference signal. In one embodiment, the timing of the reference signal will be based on the cell ID.

[0136] In step S3, the cell sends the reference signal. The timing of the reference signal will be controlled by the cell according to, for example, the cell ID.

[0137] In step S4, the user equipment receives the reference signal and processes the signal. In practice, the user equipment can receive reference signals from multiple base stations. The reference signals can be orthogonal. In some embodiments, this may mean that these reference signals are received at different times. In certain embodiments, reference signals from two different base stations can be received in the same subframe. In an alternative embodiment, reference signals from different cells can be received in different subframes. Of course, in some embodiments, the user equipment can receive reference signals from three or more base stations. It is possible to receive some reference signals from different base stations in different subframes and / or different reference signals from different base stations in the same subframe.

[0138] In step S5, based on the position of the reference signal, the user equipment can determine from which cell the signal is sent. For search purposes, these reference signals are used by the user equipment.

[0139] Refer to Figure 7, which illustrates a schematic diagram of the device in a cell. The device includes an active mode controller 700. The active mode controller will control whether the cell is in an active state or a sleep mode. This may be in response to information determined by the cell itself and / or information received, for example, from a radio network controller. The active mode controller 700 is configured to provide information to a reference signal timing controller 702. The reference signal timing controller 702 is arranged such that, in the sleep mode, the cell ID is used to control the timing of the reference signal, i.e., when and on which resources to transmit the reference signal. The cell ID can be stored in a memory 704.

[0140] The reference signal timing controller 702 is configured to provide timing information to a reference signal block 706. This provides a reference signal with timing information to a transmitter 708, which transmits the reference signal with the required timing information.

[0141] Now refer to Figure 8 , which illustrates the device of a user equipment. The device includes a receiver 800, which is arranged to receive reference signals from one or more cells. A processor 802 is configured to process the reference signals and can determine from which cell each respective reference signal is received. This can be determined from the cell ID. This information can be provided to a cell selection block 804, which can use the information in decisions regarding cell selection and handover.

[0142] It can be understood that one or more blocks as shown in Figure 7 or 8 can be provided by at least one processor and / or at least one memory. The same or different processors and / or memories can provide different functions. It is worth mentioning that, in alternative embodiments, one or more modules as shown in Figure 7 or 8 can be provided by appropriate circuitry and / or hardware arrangements.

[0143] The DTX mode is an example of an inactive or low-activity mode. Alternative embodiments can be used, which have any other suitable inactive or low-activity mode. The sleep state can be a state in which one or more components of the base station may be turned off, set to a standby state or not used. In one embodiment, the sleep state can be a state in which no signals are transmitted except for one or more reference signals. The sleep state consumes less energy than the inactive state.

[0144] It is worth mentioning that, in the case where the base station supports multiple carrier options, one or more carrier options may be put into the sleep state. In this alternative, one or more carrier options can be in the active state while one or more carrier options are in the sleep state.

[0145] In some embodiments, the active state can be considered the normal operating mode of the base station.

[0146] In some embodiments, a cell is referenced. In some embodiments, the teachings may be applied by a network node. The network node may be a base station or the like.

[0147] In some embodiments, a user equipment may receive mode information that indicates when a cell is in a less active or dormant mode. This information may be provided directly or indirectly. For example, when the state of a first cell changes to a less active mode, the mode information may be provided. However, in some embodiments, unless the information received by the user equipment indicates that the serving cell is in an active mode, the user equipment assumes that the cell is in a less active mode. Of course, in some embodiments, the user equipment may receive information that indicates when the active mode starts and when the active mode ends.

[0148] Reference is made to a specific configuration. Some embodiments may be applicable to other configurations.

[0149] Reference is made to various channels. It is worth mentioning that other embodiments may be used with other channels.

[0150] Reference is made to a so-called new carrier type. It is worth mentioning that what it refers to may be replaced by future nomenclature. It is worth mentioning that other embodiments may optionally or additionally be used for any other carrier.

[0151] It should be noted that although the embodiments have been described with respect to LTE, similar principles may be applied to any other communication system or to further developments of LTE. Thus, although the description of some of the above embodiments refers to certain example architectures, technologies, and standards of a wireless network, the embodiments may be applied to any other suitable form of a communication network, as compared to what is shown and described herein.

[0152] In the above embodiments, reference signals PSS, SSS, and CSR are referenced. One or more of these signals may be omitted. It is worth mentioning that any other suitable reference signals may optionally or additionally be used.

[0153] In some embodiments, only one reference signal may be required. In other embodiments, multiple reference signals may be required.

[0154] As above, reference is made to the reference signals of a base station. In some embodiments, the reference signal may be provided by a cell. In some embodiments, a base station may serve one or more cells. In some embodiments, as described above, the resource elements of the PSS / SSS may be determined by the physical cell ID.

[0155] In some embodiments, an association between a) a cell (cell ID) and b) a resource element is provided. Three reference signals (PSS and SSS / CRS) are transmitted on the resource element.

[0156] In some embodiments, in addition to the resource elements within a PRB, the subframes in which reference signals are transmitted are associated with the cell (i.e., depending on the cell ID). In some embodiments, the reference signals from a first cell may be associated with a first subframe, and the reference signals from a second cell may be associated with a second subframe. Assuming a duty cycle of 5 subframes, a given cell (cell ID) can be associated with 5 possible different subframes.

[0157] In some embodiments, the PSS / SSS and CRS signals (with a predefined number of repetitions in a given duty cycle) composed of bursts are used for neighboring cell discovery to achieve fast and efficient cell search during the eNB sleep state. If in DTX on mode, (where the eNB is in the sleep mode but only transmits PSS / SSS / CRS), a sleep type of the downlink DL time period is defined for DL LTE. During this period, only CRS and PSS / SSS are transmitted on the downlink to support UE features such as synchronization and network cell selection in the sleep state.

[0158] In some embodiments, different cells transmit their PSS / SSS signals in different OFDM symbols within a subframe, thus ensuring the orthogonality of discovery between different cells. Additionally, further orthogonality is provided by introducing an additional correlation between the cell ID and the timing of PSS / SSS in the burst (within the subframe and between different subframes) and / or the CRS frequency shift.

[0159] The required data processing apparatus and base station apparatus functions, communication equipment, and any other suitable equipment can be provided by one or more data processors. The functions of each described terminal can be provided by a separate processor or an integrated processor. The data processor can be of any type suitable for the local technical environment and can include one or more general-purpose computers, special-purpose computers, microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), gate-level circuits, and processors based on a multi-core processor architecture, without being limited by the examples. The data processing can be distributed among multiple data processing modules. The data processor can be provided, for example, by at least one chip. Appropriate storage capacity can also be provided in the relevant equipment. The memory can be of any type suitable for the local technical environment and can be implemented using any suitable data storage technology, such as semiconductor-based storage devices, magnetic memory devices and systems, optical storage devices and systems, fixed memory, and removable memory.

[0160] In general, the various embodiments may be implemented in hardware or special purpose circuitry, software, logic devices, or any combination thereof. Certain aspects of the present invention may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device, but the present invention is not limited thereto. Although aspects of the present invention may be illustrated and described as block diagrams, flowcharts, or using some other graphical representation, it is readily understood that the blocks, devices, systems, techniques, or methods described herein may be implemented as non-limiting examples, hardware, software, firmware, special purpose circuitry or logic, general purpose hardware or controllers or other computing devices, or some combination thereof. Software may be stored on physical media such as memory chips, or memory blocks implemented by a processor, magnetic media such as hard disks or floppy disks, and optical media such as DVDs and data and its variants, CDs.

[0161] By way of illustration and not limitation, the above provides a comprehensive and detailed exemplification of the present invention. However, those skilled in the art may obtain various modifications and variations based on the above description, reading in conjunction with the accompanying drawings and the appended claims. However, all such and similar variations according to the teachings of the present invention will still fall within the scope of the present invention as defined by the claims. There are embodiments that include combinations of one or more of any of the other embodiments described above.

Claims

1. A communication method, comprising: Receiving (S4) at least one periodic reference signal from a first cell in a dormant state and receiving (S4) at least one periodic reference signal from a second cell in a dormant state within the same or different subframes of a subframe group, wherein the at least one periodic reference signal from the first cell is associated with a resource element of the subframe group, the resource element being different from the resource element associated with the at least one periodic reference signal from the second cell, each cell having an identifier associated therewith, the reference signal from each cell including a primary synchronization signal and / or a secondary synchronization signal, wherein the primary synchronization signal and / or the secondary synchronization signal is transmitted using four unique symbol pairs, wherein the four unique symbol pairs are {1, 2}, {5, 6}, {8, 9}, {12, 13}.

2. A communication method, comprising: Causing (S3) at least one periodic reference signal to be transmitted from a first cell in a dormant state within a subframe of a subframe group, and the at least one periodic reference signal being provided on a resource element different from the resource element used by a second cell in the subframe group, the first cell being in a dormant state, the reference signal including a primary synchronization signal and / or a secondary synchronization signal, wherein the primary synchronization signal and / or the secondary synchronization signal is transmitted using four unique symbol pairs, wherein the four unique symbol pairs are {1, 2}, {5, 6}, {8, 9}, {12, 13}.

3. The method according to claim 2, wherein the subframe group includes a plurality of consecutive subframes.

4. The method according to claim 3, wherein the subframe group is repeated x times to provide a burst, x being an integer.

5. A communication device, characterized in that, The apparatus comprises: A component (800) for receiving at least one periodic reference signal from a first cell in a dormant state and receiving at least one periodic reference signal from a second cell in a dormant state within the same or different subframes of a subframe group, wherein the at least one periodic reference signal from the first cell is associated with a resource element of the subframe group, the resource element being different from the resource element associated with the at least one periodic reference signal from the second cell, each cell having an identifier associated therewith, the reference signal from each cell including a primary synchronization signal and / or a secondary synchronization signal, wherein the primary synchronization signal and / or the secondary synchronization signal is transmitted using four unique symbol pairs, wherein the four unique symbol pairs are {1, 2}, {5, 6}, {8, 9}, {12, 13}.

6. A communication device, characterized in that, The apparatus comprises: A component (708) for causing at least one periodic reference signal to be transmitted from a first cell within a subframe of a subframe group, and the at least one periodic reference signal is provided on resource elements different from those used by a second cell in the subframe group, the first cell being in a dormant state, the reference signal including a primary synchronization signal and / or a secondary synchronization signal, wherein the primary synchronization signal and / or the secondary synchronization signal is transmitted using four unique symbol pairs, and the four unique symbol pairs are {1,2}, {5,6}, {8,9}, {12,13}.

7. The apparatus according to claim 6, wherein the subframe group includes a plurality of consecutive subframes.

8. The apparatus according to claim 6, wherein the subframe group is repeated x times to provide a burst, and x is an integer.

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