BR112017001564B1 - METHOD, IN A BASE STATION OPERATING IN A WIRELESS COMMUNICATIONS NETWORK, FOR FACILITATING WIRELESS SYNCHRONIZATION WITH A NEIGHBORING BASE STATION, BASE STATION, AND, COMPUTER READABLE STORAGE MEDIUM - Google Patents

Abstract

METHOD FOR FACILITATING WIRELESS SYNCHRONIZATION, BASE STATION, BASE STATION APPARATUS, COMPUTER PROGRAM PRODUCT, AND, COMPUTER READABLE MEDIA. Methods for enabling and disabling silencing patterns in nodes of the Radio Access Network, RAN, are described, with the purpose of allowing better detection and use of reference symbols used for synchronization. An example method for facilitating wireless synchronization with a neighboring base station is implemented at a base station operating in a wireless communications network. The method comprises determining (1110) that a first neighboring cell of a plurality of neighboring cells is interfering with, or is likely to interfere with, a signal from the second neighboring cell, which is used for synchronization. The method further comprises sending (1120), in the direction of the first neighboring cell and in response to said determination, a request for activation of a reference signal silencing pattern by the first neighboring cell.

Description

TECHNICAL FIELD

[001] The present description refers, in general, to wireless communication systems and, more specifically, refers to techniques for reducing interference in reference signals used for synchronization procedures.

FUNDAMENTALS

[002] The 3rd Generation Partnership Project (3GPP) is responsible for standardizing the Universal Mobile Telecommunications System (UMTS) and the fourth generation wireless system commonly known as Long Term Evolution (LTE). 3GPP's work on LTE is also referred to as Evolved Universal Terrestrial Access Network (E-UTRAN). LTE is a technology for performing high-speed packet-based communication that can achieve high data rates on both the downlink (the link that carries transmissions from the base station to a mobile station) and the uplink (the link that carries transmissions from a mobile station to the base station), and is designed as a next generation mobile communication system in relation to UMTS. In order to support high data rates, LTE allows for a system bandwidth of 20 MHz or up to 100 MHz when carrier aggregation is employed. LTE is also capable of operating in several different frequency bands and can operate in at least Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes.

[003] In LTE mobile broadband wireless communication systems, transmissions from base stations (referred to in 3GPP documentation as eNBs) to mobile stations (referred to as user equipment or UEs) are sent using orthogonal frequency division multiplexing (OFDM ). OFDM divides the signal into multiple subcarriers parallel in frequency. Figure 1 illustrates the physical resource in LTE downlink. The basic transmission unit in LTE is a resource block (RB) which, in its most common configuration, consists of twelve subcarriers and seven OFDM symbols. The time interval of seven OFDM symbols is referred to as an “interval”. A unit of a subcarrier and an OFDM symbol is referred to as a resource element (RE), which can carry a modulated data symbol. Thus, an RB consists of 84 REs.

[004] Figure 2 illustrates the downlink subframe in LTE. An LTE radio subframe is composed of two time slots and multiple resource blocks on the frequency, with the number of RBs determining the system bandwidth. Furthermore, the two RBs in a subframe that are adjacent in time are denoted as an RB pair. Currently, LTE supports standard bandwidth sizes of 6, 15, 25, 50, 75, and 100 RB pairs.

[005] In the time domain, LTE downlink transmissions are organized into 10 millisecond radio frames, each radio frame consisting of ten equally sized subframes of length Tsubframe = 1 millisecond.

[006] The signal transmitted by an eNB in a downlink subframe can be transmitted from multiple antennas, and the signal can be received at a UE that has multiple antennas. The radio channel distorts the signals transmitted from each of the multiple antenna ports. In order to demodulate any transmissions on the downlink, a UE thus relies on reference symbols (RS) that are transmitted on the downlink. These reference symbols and their positions on the temporal frequency grid are known to the UE and can be used to determine channel estimates by measuring the effect of the radio channel on these symbols. As for Edition 11 of the 3GPP specifications for LTE, there are multiple types of reference symbols. One important type is common reference symbols (CRS), which are used for channel estimation during demodulation of control and data messages. The CRS are also used by the UE for synchronization, that is, to align the synchronization of the UE with the downlink signal received from the eNB. CRSs occur once per subframe.

[007] A key improvement on conventional cellular network implementations involves the implementation of relatively low-power “small cells” to overlay a conventional array of so-called “macrocells”. The result is often referred to as a “heterogeneous network”. Heterogeneous networks, in which macrocells and small cells have vastly different transmission energies, can be implemented in two main ways. In the first type of implementation, the small cell layer and the macrocell layer share the same carrier frequencies. This approach creates interference between the two layers. In the second type of implementation, the small cell layer and the macrocell layer are at separate frequencies.

[008] The network architecture for LTE allows messages to be sent between eNBs via an X2 interface. The eNB can also communicate with other nodes in the network, for example to the Mobility Management Entity (MME) via the S1 interface. In figure 3, the architecture involving E-UTRAN, that is, the radio access network (RAN) and the core network (CN), is shown. In current specifications for LTE systems (see, for example, “S1 Application Protocol", 3GPP TS 36.413 v12.2.0, available at www.3gpp.org), methods are specified that enable some self-organizing network (SON) functionality, wherein an eNB may request information in relation to another eNB through the MME.

[009] As noted previously, UEs use CRS transmitted by the eNB to synchronize with the eNB. Many features of 3GPP Long Term Evolution (LTE) technology, as well as other technologies, benefit from the base stations (referred to as eNBs) in the system being synchronized with each other regarding timing and transmission frequency. Synchronization of eNBs is typically done using a global navigation satellite system (GNSS), such as global positioning system (GPS), or by using network-based methods, such as IEEE 1588v2. However, when such methods are unavailable for an eNB, it is possible to use LTE reference signals transmitted by other eNBs to acquire synchronization. Such techniques are currently being discussed in 3GPP for small cells in LTE Rel-12, where a small cell can obtain synchronization from a macrocell or from other small cells.

[0010] Currently, a network interface-based signaling approach is used for synchronization purposes between eNBs. This is enabled through procedures known as the “S1: eNB Configuration Transfer” and “S1: MME Configuration Transfer” procedures, according to the following steps: • A first eNB, eNB1, generates an eNB Configuration Transfer message that contains a SON Information Transfer information element (IE). • The MME that receives the eNB Configuration Transfer message forwards the SON Information Transfer IE towards a target eNB, eNB2, indicated in the IE, through the MME Configuration Transfer message. • If the SON Configuration Transfer IE contains a SON Information Request IE defined in “Time Synchronization Information”, the receiving eNB2 may respond with an eNB Configuration Transfer message in the direction of the eNB1, including an IE of SON Information Response and Timing Synchronization Information IE, which contains Stratum Level and Synchronization State of the sending node. • The MME receiving the eNB Configuration Transfer message from eNB2 forwards it to eNB1 via via the MME Configuration Transfer message.

[0011] In summary, in an eNB Configuration Transfer message from the eNB to the MME, it is possible to indicate a target eNB ID and the SON information that is required from this target eNB. The MME will therefore forward an information request like this to the target eNB through a procedure called MME Configuration Transfer. Once the target eNB receives the request, it will respond via eNB Configuration Transfer towards the MME, which will include the information requested by the source eNB. The MME will forward the requested information to the originating eNB through a new MME Information Transfer.

[0012] If a source eNB requests time synchronization information from a target eNB, the response contained in the SON Configuration Transfer IE from the target eNB to the source eNB must include the aforementioned information elements (IEs): • Stratum Level: This is the number of hops between the eNB and the synchronization source. That is, when the stratum level is M, the eNB is synchronized with an eNB whose stratum level is M-1, which in turn is synchronized with an eNB with stratum level M-2, and so on. The eNB with stratum level 0 is the synchronization source. • Synchronization State: This is an indicator that indicates whether an eNB is currently in a synchronous or asynchronous state.

OAM architecture

[0013] The management system architecture considered for the present discussion is shown in figure 4. The node elements (NE), also referred to as eNodeB, are managed by a domain manager (DM), which is also referred to as the operation and support system (OSS). A DM can be additionally managed by a network manager (NM). Two NEs are interfaced by the X2 interface defined by the 3GPP specifications, while the interface between two DMs is referred to by the 3GPP specifications as the Itf-P2P interface. The management system can configure the network elements and can receive observations associated with the resources on the network elements. For example, a DM observes and configures NEs, while an NM observes and configures DMs, as well as NEs through the intermediate DMs.

[0014] Through configuration through the DM, NM and related interfaces, functions over the X2 and S1 interfaces can be performed in a coordinated manner across the entire RAN, eventually involving the Core Network, i.e., the MME and the S-GWs.

Radio Interface Based Synchronization (RIBS)

[0015] In recent progress in 3GPP RAN1 work, it has been concluded that it will be beneficial, for synchronization purposes, to make use of temporal frequency transmission resource patterns that are selectively muted to ensure low interference, thus enabling network nodes to RANs in need of wireless synchronization decode a synchronization reference signal that would otherwise be affected by neighboring cell interference and thus not usable. In particular, the feature elements in these muted patterns must be free from any reference signal or any other interfering signal transmissions.

[0016] 3GPP Working Group Discussion Documents R3- 140997, “LS on Status of Radio-Interface Based Synchronization” (available at http://www.3gpp.org/FTP/tsg_RAN/WG3_Iu/TSGR3_84/LSin/) and R1-142762, “LS on Radio Interface Based Synchronization” (available at http://www.3gpp.org/Liaisons/Outgoing_LSs/R1-meeting.htm), describe the agreements made by RAN1 in terms of what characteristics such standards must be.

[0017] In summary, the agreements state that the network must support the enabling of interference-protected time/frequency resource standards. These patterns may repeat in time according to a period selected from a range specified in the last of the two documents specified immediately before. It should be noted that these patterns are different from existing Near-Blank Subframe patterns, which are used for enhanced intercell interference coordination (eICIC). One difference is that, in ABS standards, reference signals are transmitted without interruption, which is one of the reasons why such standards are made of so-called “Almost” blank subframes.

[0018] The previously identified 3GPP discussion documents specify that the reference signals that a RAN node can use to achieve synchronization can be different, and that the protected interference patterns must therefore guarantee protection in the direction of all interference signals. reference. In summary, the information from these documents that is relevant to the signaling specification necessary to make the radio interface-based synchronization mechanisms work is as follows. Excerpts from R3-140997 (cited previously): Agreement: • Specifies monitoring RS(s) that include standard RS, and subframe periodicity, and offset, for both FDD and TDD Agreement: • PRS and/or CRS are used as o Monitoring RS for RIBS - FFS: Top-down selection of monitoring RS • Subframe level muting is supported for RIBS Excerpts from R1-142762 (previously cited): • For network monitoring, the following RS standard is supported by configuration - CRS only - The number of CRS ports can be 1 or 2 - CRS and PRS - The number of CRS ports can be 1 or 2 - The eNB must use a periodicity and network monitoring RS offset that can be selected from of the following recommended range of values - A range of values (>= 2) for the periodicity - Choose all or a subset from [1,280 ms, 2,560 ms, 5,120 ms, 10,240 ms] - There is no consensus in RAN1 on the periodicities additional 640 ms and 20,480 ms - FFS offset values • The maximum number of hops is kept at 3.

[0019] Although the exposed documents provide a starting point for enabling interference protection for wireless synchronization measurements, additional work is required to provide complete solutions.

SUMMARY

[0020] The agreements reached in the RAN1 working group of 3GPP leave the problem of how to enable inter-node communication aimed at coordinating the enabling of protected interference patterns unresolved. Embodiments of the techniques and apparatus currently described thus include methods for enabling and disabling silencing patterns on RAN nodes for the purpose of enabling better detection and use of reference symbols (RS) used for synchronization.

[0021] Some of these methods allow a node to request activation or deactivation of silencing patterns. In response, nodes involved in enabling RIBS silencing patterns are allowed to flexibly select the patterns and pattern period that best suit their conditions, e.g., to select the patterns and pattern periods that best match with current traffic resource demands.

[0022] According to a first aspect of the techniques and apparatus described herein, a method is implemented at a base station operating in a wireless communications network, to facilitate wireless synchronization with a neighboring base station. The method comprises determining that a first neighboring cell of a plurality of neighboring cells is interfering with, or is likely to interfere with, a signal from the second neighboring cell, which is used for synchronization. The method further comprises sending, in the direction of the first neighboring cell and in response to said determination, a request for activation of a reference signal silencing pattern by the first neighboring cell.

[0023] According to a second aspect, another method is implemented in a base station operating in a wireless communications network, to facilitate wireless synchronization by a neighboring base station. This method includes receiving a request to activate a reference signal muting pattern for a cell supported by the base station and activating the reference signal muting pattern in response to the request.

[0024] According to a third aspect, another method is implemented in a control node operating in a wireless communications network, to facilitate wireless synchronization by a first base station with a first neighboring cell of a plurality of neighboring cells, the method comprising receiving a first message from the first base station, the first message indicating which mutes the reference signal by at least one second neighboring cell of the plurality of neighboring cells is necessary. The method further comprises sending a second message to at least one second base station corresponding to the second neighboring cell, the second message requesting the activation of a reference signal muting pattern for the second neighboring cell.

[0025] According to a fourth aspect, a base station is configured to operate in a wireless communications network and to facilitate wireless synchronization with a neighboring base station. The base station is adapted to determine that a first neighboring cell of a plurality of neighboring cells is interfering with, or is likely to interfere with, a signal from the second neighboring cell, which is used for synchronization. The base station is further adapted to send in the direction of the first neighboring cell, in response to said determination, a request for activation of a reference signal silencing pattern by the first neighboring cell.

[0026] According to a fifth aspect, a base station is configured to operate in a wireless communications network and to facilitate wireless synchronization by a neighboring base station, and is adapted to receive a request for activation of a silencing of the reference signal for a cell supported by the base station. The base station is further adapted to activate the reference signal muting pattern in response to the request.

[0027] According to a sixth aspect, a control node is configured to operate in a wireless communications network and to facilitate wireless synchronization between base stations. The control node is adapted to receive a first message from a first base station, the first message indicating that silencing of the reference signal by at least one second neighboring cell of the plurality of neighboring cells is necessary, and is further adapted to sending a second message to at least one second base station corresponding to the second neighboring cell, the second message requesting the activation of a reference signal muting pattern for the second neighboring cell.

[0028] Other embodiments of the techniques and apparatus described herein include computer program products comprising program instructions for carrying out one or more of the methods summarized above and/or variants thereof, as well as computer readable media incorporating any one or more more of these computer program products.

BRIEF DESCRIPTION OF FIGURES

[0029] Figure 1 illustrates temporal frequency features in a system that uses Orthogonal Frequency Division Multiplexing (OFDM).

[0030] Figure 2 illustrates a subframe in an LTE system.

[0031] Figure 3 illustrates a simplified version of the E-UTRAN system architecture.

[0032] Figure 4 illustrates a management architecture.

[0033] Figure 5 is another view of the E-UTRAN system.

[0034] Figure 6 illustrates components of an example user equipment.

[0035] Figure 7 illustrates components of an example base station.

[0036] Figure 8 shows an example scenario in which the currently described techniques can be employed.

[0037] Figure 9 is a signal flowchart that illustrates some embodiments of the techniques currently described.

[0038] Figure 10 is another signal flowchart, again illustrating some modalities of the currently described techniques.

[0039] Figure 11 is a process flowchart illustrating an example method in accordance with some of the techniques described.

[0040] Figure 12 is another process flowchart that illustrates an example method in accordance with some of the techniques described.

[0041] Figure 13 is yet another process flowchart that illustrates an example method in accordance with some of the techniques described.

[0042] Figure 14 illustrates components of an example base station or control node, in accordance with various embodiments of the currently described techniques and apparatus.

[0043] Figures 15, 16, 17 are functional representations of base stations and an example control node, in accordance with various embodiments of the techniques and apparatus currently described.

DETAILED DESCRIPTION

[0044] In the discussion that follows, specific details of particular embodiments of the currently described techniques and apparatus are presented for explanatory purposes and without limitation. Those versed in the technique realize that other modalities can be used, in addition to these specific details. Furthermore, in some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as not to obscure the description with unnecessary detail. Those skilled in the art will realize that the functions described can be implemented in one or several nodes.

[0045] Some or all of the described functions can be implemented using hardware circuitry systems, such as analog and/or discrete logic gates interconnected to perform a specialized function, ASICs, PLAs, etc. Likewise, some or all of the functions may be implemented using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. When nodes that communicate using the air interface are described, it will be seen that these nodes also have adequate radio communications circuitry. Furthermore, the technology may further be envisaged to be incorporated integrally into any form of computer-readable memory, including non-transitory embodiments, such as solid-state memory, a magnetic disk, or optical disk, that contain an appropriate set of instruction instructions. computer that will cause a processor to perform the techniques described here.

[0046] Hardware implementations may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware circuit system (e.g., digital or analog) that includes, but is not limited to , application-specific integrated circuits (ASIC) and/or field-programmable gate arrays (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

[0047] In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer, processor and controller may be used interchangeably. When provided by a computer, processor, or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which can be shared or distributed. Furthermore, the term “processor” or “controller” also refers to other hardware capable of performing such functions and/or running software, such as the hardware example mentioned above.

[0048] References throughout the specification to “an embodiment” or “the embodiment” mean that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in an embodiment” or “in the modality” in various places throughout the specification are not necessarily all referring to the same modality. Additionally, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0049] Although the following examples are described in the context of LTE systems, the principles described in the following description can equally be applied to other cellular networks. Other wireless systems, including WCDMA, WiMax, UMB, and GSM, may also benefit from exploring the techniques described here. Note also that the use of terminology such as eNodeB and UE should be considered non-limiting, and does not necessarily imply a certain hierarchical relationship between the two; In general, an “eNodeB” can be considered as a first wireless device and a “UE” as a second wireless device, where these two devices communicate with each other over a radio channel. Similarly, when talking about signaling over an X2 cluster, the solutions are not necessarily limited to communication between eNBs, but the communication nodes can be any node that terminates the cluster transfer interface over which the described information is transmitted.

[0050] Figure 5 is another view of an E-UTRAN architecture, as part of an LTE-based communications system 2. Nodes in the core network 4 include one or more Mobility Management Entities (MMEs) 6, which are key control nodes for the LTE access network, and one or more Service Connection Ports (SGWs) 8, which route and forward user data packets while also acting as mobility anchors. The MMEs 6 and SGWs 8 communicate with base stations 10 referred to in LTE as eNBs, over interfaces specified by 3GPP standards, such as the S1 interface. The eNBs 10 may include two or more of the same or different categories of eNBs, e.g., macro eNBs, and/or micro/pico/femto eNBs. The eNBs 10 communicate with each other over an interface, for example, an X2 interface. The S1 interface and the X2 interface are defined in the LTE standard. A UE 12 may receive downlink data from and send uplink data to one of the base stations 10, with this base station 10 being referred to as the serving base station of the UE 12. It should be appreciated that although the techniques described here can be applied in the context of an E-UTRAN network, for example, as illustrated in figures 3 and 5, the techniques can also be applied in other network contexts, including UTRA networks, or even in non-hierarchical communication , such as in an ad-hoc network or in a so-called device-to-device scenario.

[0051] In some of the embodiments described herein, the non-limiting terms “user equipment” and “UE” are used. A UE, as this term is used herein, can be any type of wireless device capable of communicating with a network node or another UE over radio signals, including an MTC device or M2M device. A UE may also be referred to as a mobile station, a radio communication device, or a target device, and the term is intended to include device-to-device UEs, machine-type UEs, or UEs capable of machine-to-machine communication, sensors equipped with a UE, wireless capable desktop computers, mobile terminals, smart phones, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, customer premise wireless equipment (CPE), etc. .

[0052] Figure 6 shows a user equipment (UE) 12 that can be used in one or more of the systems described here. The UE 12 comprises a processing module 30 that controls the operation of the UE 12. The processing module 30, which may comprise one or more microprocessors, microcontrollers, digital signal processors, specialized digital logic, etc., is connected into a module receiver or transceiver 32 with associated antenna(s) 34 that are used to receive signals from and/or to transmit signals to a base station 10 in network 2. User equipment 12 also comprises a memory circuit 36 which is connected to the processing module 30 and which stores program code and other information and data required for the operation of the UE 12. Together, the processing module and memory circuit may be referred to as a “processing circuit”, and are adapted, in various embodiments, to perform one or more of any of the UE-based techniques described below.

[0053] In the description of some embodiments below, the generic terminology “radio network node” or simply “network node (NW node)” is used. These terms refer to any type of wireless network node, such as a base station, a radio base station, a transceiver base station, a base station controller, a network controller, an Evolved Node B (eNB), a B Node, a relay node, a positioning node, an E-SMLC, a local server, a repeater, an access point, a radio access point, a Radio Unit Remote Radio Head (RRH) Remote Radio (RRU), a multistandard radio (MSR) radio node, such as MSR BS nodes in distributed antenna system (DAS), a SON node, an O&M, OSS, or MDT node, a core network node, a MME, etc.

[0054] Figure 7 shows a base station 10 (for example, a NodeB or an eNodeB) that can be used in the described example embodiments. It will be appreciated that, although a macro eNB, in practice, will not be identical in size and structure to a micro eNB, these different examples of base station 10 will generally include similar or corresponding components, although the details of each of these components may vary to accommodate the different operational requirements of a particular modality.

[0055] The illustrated base station 10 comprises a processing module 40 that controls the operation of the base station 10. The processing module 40, which may comprise one or more microprocessors, microcontrollers, digital signal processors, specialized digital logic, etc. , is connected to a transceiver module 42 with associated antenna(s) 44, which are used to transmit signals to, and receive signals from, user equipment 12 on the network 2. The base station 10 also comprises a circuit memory circuit 46 which is connected to the processing module 40 and which stores program and other information and data required for the operation of the base station 10. Together, the processing module 40 and the memory circuit 46 may be referred to as a “circuit” processing", and are adapted, in various embodiments, to perform one or more of the network-based techniques described below.

[0056] The base station 10 also includes components and/or circuitry 48 to allow the base station 10 to exchange information with other base stations 10 (e.g., via an X2 interface) and components and/or circuitry 49 to allow the base station 10 to exchange information with nodes in the core network 4 (e.g., via the S1 interface). It will be appreciated that base stations for use in other types of networks (e.g., RAN UTRAN or WCDMA) will include components similar to those shown in Figure 7 and appropriate interface circuitry 48, 49 to enable communications with other network nodes in these types of networks (e.g. for communications with other base stations, mobility management nodes and/or nodes in the core network).

[0057] It will be appreciated that other nodes in the communication network may have a structure that is similar to that illustrated in Figure 7, with the transceiver module 42 omitted in those nodes that are not radio base stations. Nodes in the core network may have a RAN network interface circuit in place of the core network interface circuit 49, in some embodiments.

[0058] As noted previously, many features of 3GPP Long Term Evolution (LTE) technology, as well as other technologies, benefit from base stations (referred to as eNBs) in the system that are synchronized with each other relative to synchronization and transmission frequency. Synchronization of eNBs is typically done using a global navigation satellite system (GNSS), such as global positioning system (GPS), or by using network-based methods, such as IEEE 1588v2. However, when such methods are unavailable for an eNB, it may be possible to use LTE reference signals transmitted by other eNBs to acquire synchronization. Such techniques are currently being discussed in 3GPP for small cells in LTE Rel-12, where a small cell can obtain synchronization from a macrocell or from other small cells.

[0059] The problem addressed by the currently described techniques and apparatus is how to enable a mechanism that allows the RAN node in need of synchronization to correctly detect and use the most appropriate synchronization reference signal. More particularly, these techniques facilitate the enabling of an interference-protected resource pattern in which the node can monitor RS synchronization and synchronize with it. A pattern like this will also be referred to herein as a “squelch pattern” or “RIBS squelch pattern”.

[0060] Enabling a silencing pattern should depend on whether there is a node in need of interference protection for synchronization purposes. In fact, keeping a set of temporal frequency resources muted in any cell generally results in a loss of resources and a decrease in system performance. Therefore, the techniques described here allow the activation and deactivation of relevant interfering cell silencing patterns, depending on whether there are nodes in need of synchronization with other cells that will benefit from such interference-protected patterns.

[0061] Another problem that the currently described techniques and apparatus address is how to achieve coordination of silencing patterns and activation of silencing patterns. Namely, the Radio Access Network (RAN) node responsible for activating silencing patterns is the only node aware of the traffic demand on the node at the time of activation. Therefore, it must be up to this node to decide the amount of silencing to apply that is feasible, given the demand for traffic that is currently maintained. At the same time, it will be beneficial to address methods that enable a greater number of cells interfering with RS synchronization at the same time to activate coordinated silencing patterns, that is, silencing patterns that share the same silencing features.

[0062] In the 3GPP discussion document R3-14121, “Discussion on How to Support RIBS” (available at http://www.3gpp.org/ftp/Meetings_3GPP_SYNC/RAN3/Docs/), solutions that attempt to address RIBS signaling Silencing pattern information for RIBS purposes is presented. However, all presented solutions are subject to several shortcomings. First, the proposed solutions are sub-optimal and inefficient because they are all based on an indication, sent from the node in need of synchronization to the node selected for synchronization, where the indication informs the receiving node that synchronization will occur with one of its cells. This indication is unnecessary because, upon selection of a synchronization node, there are no changes in the operating mode of the node that is providing synchronization signals. Therefore, this indication results in unnecessary signaling. Second, these solutions are non-scalable and inefficient because they are based on communicating node silencing patterns in need of synchronization to the interfering nodes. The node in need of synchronization is unaware of the load demand conditions of the interfering nodes and will not be able to determine precisely how much resource silencing the interfering node will be able to bear. Furthermore, in the event that a second node in need of synchronization has requested the same interfering node to activate a different silencing pattern, the interfering node may either need to reject the request due to an excessive overall amount of resources for silencing or accept it. the same, with the consequence of a greater loss of capacity due to different, possibly non-overlapping, silencing patterns.

[0063] Embodiments of the currently described invention enable the exchange of information about the possibility of activating silencing patterns in interfering cells that would allow a node that needs to correctly and timely decode a synchronization signal to do so.

[0064] These modalities also allow activation and deactivation of silencing patterns to occur only when necessary. Namely, resources are silenced only when there is a need to reduce interference for the purpose of synchronization, in some embodiments, avoiding unnecessary losses in capacity.

[0065] Embodiments also allow a node receiving a request to silence resources to select an appropriate silencing pattern according to its traffic conditions and cell state.

[0066] In order to explain a first method according to some embodiments of the invention, an example scenario is detailed here. In particular, the scenario takes the LTE system as an example, and consists of a case in which an eNB detects a cell reference signal suitable for synchronization, in which the synchronization source has a lower stratum number than other detected RSs. (It will be noted that, by convention, the lower the stratum level, the higher the signal accuracy is relative to an elementary synchronization source such as GNSS). In this scenario, it will be beneficial if other cells that interfere with the synchronization signal can adopt a silencing pattern in which all RSs are silenced in certain subframes, according to a certain pattern that can repeat with a certain period, for example, as in 3GPP documents R3-140997 and R1-142762 mentioned above.

[0067] Figure 8 illustrates a possible scenario in which such radio interface-based synchronization (RIBS) may be necessary. In figure 8 it can be seen that Cell S emits a reference signal that is synchronized in GNSS. eNB C, which serves Cell C and may serve mobile station MS A, for example, may deduce such information by means of, for example, S1 signaling of the SON Information IE, namely, by receiving a SON Information IE. Time Synchronization where the Stratum Level IE was set to “0” as per specifications in 3GPP TS 36.413, v12.2.0.

[0068] Similarly, eNB A, which serves Cell A, may deduce that Cell C is a better synchronization source than Cell B and may attempt to use Cell C's RS to synchronize. However, in order to achieve correct RS detection from Cell C, eNB A needs to be protected from Cell B interference.

[0069] For this reason, RAN1 agreed that it will be beneficial to establish a subframe silencing pattern, that is, a pattern of subframes in which all RS signals from interfering cells are silenced.

[0070] As a consideration of a first method to be detailed below, it is considered that the set of silencing patterns available for activation in cells of a RAN node does not change frequently. Therefore, these patterns can be configured from a centralized entity, such as OAM, so that the RAN node has a set of silencing patterns available for activation at any given time.

[0071] According to some embodiments of the techniques detailed below, silencing patterns in cells of a RAN node are activated and deactivated only when necessary. Such activation and deactivation must be triggered by specific events. For example, if a RAN node decides to perform wireless synchronization using the RS signal from a neighboring cell that is considered the best available synchronization source, and if such synchronization requires other neighboring cells to mute (or reduce interference on) time frequency resources In order to properly decode the signal, then silencing patterns in these other neighboring cells need to be activated. Additionally, such patterns will need to be deactivated as soon as they are no longer needed, for example, if the RS synchronization source is no longer available or if a better synchronization signal does not require silencing of neighboring cells to become available.

[0072] Activation and deactivation of silencing patterns are both important. In fact, keeping squelch patterns enabled when squelch patterns are not needed will incur a loss of temporal frequency resources and therefore a degradation of system performance and reduced capacity.

[0073] Based on the above observations, a way to achieve activation and deactivation of silencing patterns may include the following steps, all or some of which can be used in various embodiments: • Announcing the availability of silencing patterns through signaling dedicated or by improving existing signage. For example, in the case of LTE, this may consist of enhancing the SON Information Response IE (received as a result of sending a SON Information Request IE defined in “Time Synchronization Information”) with new information that indicates availability of silencing patterns. • Enable a RAN node (for example, an eNB that suffers from interference from neighboring cells) to request that neighboring RAN nodes activate muting patterns, either through dedicated signaling or by enhancing existing signaling. For example, in the case of LTE, this may consist of enhancing the SON Information Request IE with information that indicates an activation request. The RAN node can also request the specific resources that should be silenced, that is, the pattern and frequency. • Enable a RAN node (e.g., an aggressor eNB) to signal silencing patterns and pattern period through dedicated signaling or by enhancing existing signaling. For example, in the case of LTE, this may consist of enhancing the SON Information Response IE with new information that indicates a chosen mute pattern, a pattern period, and other related information. • Enable a RAN node (e.g., an eNB) to request disabling of squelch patterns through dedicated signaling or by enhancing existing signaling. For example, in the case of LTE, this may consist of enhancing the SON Information Request IE with information that requests deactivation of mute patterns.

[0074] In the case of an LTE system, the exposed steps can be achieved through the example procedures shown in figure 9, which illustrate an example signaling procedure to enable/disable silencing patterns for RIBS.

[0075] Figure 9 can be described as follows:

[0076] Messages 1-2) An eNB1 in need of synchronization detects one or more cells from eNB2 and eNB3 and sends an eNB Configuration Transfer message with SON Information Request IE set in “Time Synchronization Information”. for eNB2 and eNB3. The SON Information Request IE will be transparently forwarded as part of an MME Configuration Transfer to the target eNB2 and eNB3.

[0077] Messages 3-4) eNB 2 and eNB3 respond with an eNB Configuration Transfer message that contains the SON Information Response IE. This IE contains information, just like the Time Sync Information IE, and, in addition, it contains a new optional indicator that declares whether RIBS mute patterns are available for activation or not (for example, mute patterns can are not available because they are not supported on the receiving eNB or because traffic conditions are such that no muting can be supported). The information will be forwarded to eNB1 in MME Configuration Transfer messages.

[0078] Messages 5-6) eNB1 evaluates which RS signals between eNB2 and eNB3 cells are the best available. Such an assessment can be made based on parameters such as signal strength, eNB stratum level, synchronization state. Considering that one of the eNB3 cells is the best synchronization source, eNB1 determines that, for correct RS detection from eNB3, RS signals coming from eNB2 need to be silenced. Therefore, eNB1 sends an eNB Configuration Transfer message in the direction of eNB2 with a SON Information Request IE set to a new value, for example, “Enable RIBS Default”.

[0079] The message may also contain a list of cells to which the silencing pattern should be applied, depending on which cells eNB1 considers to be the strongest interfering cells. Furthermore, the message may also contain the set of features that should be muted, for example, subframe pattern and periodicity. Multiple options for such silencing may be provided with some of the options being subsets of others.

[0080] Messages 7-8) eNB2, namely the interfering eNB, selects the pattern and pattern periodicity that best adapts to its conditions, such as traffic load, and enables such pattern for the cells indicated by eNB1. eNB2 responds with an eNB Configuration Transfer message in the direction of eNB1, where the SON Information Response IE contains characteristics of RIBS silencing patterns and list of cells for which the patterns have been enabled.

[0081] Messages 9-10) At a later time, it may occur that silencing of eNB2 cells is no longer necessary. For example, eNB1 may not need the RS of eNB3 as a synchronization source or, in fact, it may occur that signals from eNB3 become unavailable. In this case, eNB1 may request disabling of the mute patterns via an eNB Configuration Transfer message to the direction of eNB2 when the SON Information Request IE or another new or existing IE has been set to a new value, such as “Disable RIBS Default”. Optionally, a list of cells for which deactivation needs to occur can be specified.

[0082] The procedure described in figure 9 follows two simple and advantageous principles, namely: reusing existing procedures to exchange information about RIBS silencing patterns and enabling the activation and deactivation of silencing patterns.

[0083] Note that, by reusing existing procedures, it is possible to save signaling messages. For example, as shown in Figure 9, a SON Information Response IE may contain both “time synchronization information” and an indication of the availability of RIBS silencing patterns.

[0084] In a variation of the above method, the RAN node that receives the silencing pattern activation request does not respond with a silencing pattern, but only with a pattern period. The consideration in this case will be that silencing patterns are configured on each RAN node in a given neighborhood in such a way that each node knows which pattern is supported by a node on which a wake-up request is sent.

[0085] In another variation of the exposed method, the exchange of information regarding the activation and deactivation of silencing patterns can occur through the X2 interface. Numerous procedures can be used to enable such information exchange, for example: X2: Load Information, X2: Resource Information Request/Response/Update, X2 Configuration Request/Response, eNB Configuration Update.

[0086] An example of how such a procedure can be enabled over X2 is provided in figure 10, which shows an example of the exchange of information in relation to RIBS silencing patterns over X2.

[0087] In figure 10, it is considered that the signaling that enables eNB1 to discover which node is the best source of synchronization has already occurred. Such signaling may consist of the reuse of messages S1: eNB Configuration Transfer and S1: MME Configuration Transfer or it may consist of new X2 signaling that carries equivalent information.

[0088] It is also considered that eNB1 knows whether support for RIBS silencing patterns is available in eNB2 and eNB3. This can be achieved through the techniques outlined previously, or through new signaling about X2.

[0089] Figure 10 can be described as follows:

[0090] Message 1: RIBS mute pattern activation is shown in message 1 and is achieved by enhancing the LOAD INFORMATION message and adding a new code value in the IE Invoke Indication. Such a new value can be defined in “Activate RIBS Default” or any equivalent value that triggers an activation request. The activation request can be sent to one or more cells that can be identified in the message by their Cell IDs. The request may also include a requested muting pattern and periodicity or a set of multiple patterns and periodicities. If multiple patterns are provided, some patterns and periodicities may be a subset of others.

[0091] Message 2: eNB analyzes whether silencing patterns can be activated. If this is possible, it enables silencing patterns and resends silencing pattern structures, pattern periods, and the cell identifier to which each of the specified patterns applies in a LOAD INFORMATION message back to eNB1.

[0092] Message 3: In the case where mute patterns originating from eNB2 no longer need to be active, eNB1 may send a message silencing. This new value can be set, for example, in “Disable RIBS Default” or any equivalent value that triggers a deactivation request. The deactivation request can be sent to one or more cells that can be identified in the message by their Cell IDs.

[0093] In view of the discussion presented previously, it will be appreciated that the process flowcharts in figures 11-13 illustrate examples of methods carried out in accordance with the techniques currently described.

[0094] Figure 11, for example, illustrates a method in a base station operating in a wireless communications network, to facilitate wireless synchronization with a neighboring base station. As shown in block 1110, the method includes determining that a first neighboring cell of a plurality of neighboring cells is a desired synchronization source. The method further includes determining that a second neighboring cell of the plurality of neighboring cells is interfering with, or is likely to interfere with, a signal from the first neighboring cell, which is used for synchronization, in the manner shown in block 1120. In response, In the manner shown in block 1130, a request for activation of a reference signal silencing pattern by the second neighboring cell is sent in the direction of the second base station. In some embodiments, the request for activation is sent to a control node in the wireless communications network, wherein the control node controls a base station corresponding to the second cell. In other embodiments, the request for activation is sent directly to the base station corresponding to the second cell.

[0095] As shown in blocks 1140 and 1150, the method further includes subsequently determining that the signal from the first neighboring cell is not needed or unavailable for synchronization and, in response, sending a message, in the direction of the second neighboring cell, which indicates that the reference signal muting pattern can be disabled.

[0096] In some embodiments of the illustrated method, determining that the first neighboring cell is a desired synchronization source comprises receiving synchronization information from at least the first neighboring cell, the synchronization information indicating at least one of a stratum level, and a synchronization state, and evaluate the received synchronization information. In some embodiments, determining that the first neighboring cell is a desired synchronization source is based, at least in part, on a signal strength of a signal received from the first neighboring cell.

[0097] Some embodiments further comprise receiving an indication whether a reference signal silencing pattern is available for the second neighboring cell. In these embodiments, sending the request to activate the reference signal silencing pattern is responsive to the reception of said indication. The indication may comprise or be associated with an identification of one or more silencing patterns available for the second neighboring cell, in some embodiments. In these and other embodiments, the request for activation of the reference signal silencing pattern includes a list of cells to which a silencing pattern is to be applied and/or includes an identification of one or more resources that are to be silenced. This resource identification may comprise a subframe pattern, or a periodicity pattern, or both.

[0098] Although not shown in figure 11, synchronization can be performed based on the signal coming from the first neighboring cell. In some embodiments, this may be based on receipt of information that identifies which resources are being silenced or should be silenced by the second neighboring cell.

[0099] Figure 12 illustrates a related method, in a base station operating in a wireless communications network, to facilitate wireless synchronization by a neighboring base station. As shown in blocks 1210 and 1220, the illustrated method includes receiving a request for activation of a reference signal muting pattern for a cell supported by the base station and activating the reference signal muting pattern in response to the request. In some embodiments the request for activation is received from another base station via a base station to base station interface. In still others, the request for activation is received from a control node in the wireless communications network. As shown in blocks 1230 and 1240, a request to deactivate the reference signal mute pattern is subsequently received and the reference signal mute pattern is deactivated in response.

[00100] Although not shown in Figure 12, the illustrated operations may be preceded, in some embodiments, by receiving a request for synchronization information and responding with synchronization information that includes at least an indication that one or more muting patterns of the reference signal are available. The timing information may include an identification of one or more features that are muted in at least one first muting pattern of the reference signal; this identification may comprise a subframe pattern, or a pattern periodicity, or both.

[00101] Figure 13 illustrates a method, implemented in a control node operating in a wireless communications network, to facilitate wireless synchronization by a first base station with a first neighboring cell of a plurality of neighboring cells. As shown in block 1310, the method includes receiving a first message from the first base station, the first message indicating that silencing of the reference signal by at least one second neighboring cell of the plurality of neighboring cells is necessary. As shown in block 1320, the method continues by sending a second message to at least one second base station corresponding to the second neighboring cell, the second message requesting the activation of a reference signal muting pattern for the second neighboring cell.

[00102] As discussed previously, the various techniques described above can be implemented at a base station or other node, typically using a programmed processing node. Figure 14 illustrates an example of a processing node 100, as may be found in a base station or control node, in the manner discussed previously. It will be appreciated that the processing circuits of figure 14, as detailed below, may correspond, in whole or in part, to the processing circuits illustrated in figure 7, for example.

[00103] A computer program for controlling node 100 to perform a method incorporating any of the currently described techniques is stored in a program store 130, which comprises one or several memory devices. Data used during performance of a method incorporating the present invention is stored in a data store 120, which also comprises one or more memory devices. During performance of a method embodying the present invention, program steps are located and loaded from program store 130 and executed by a Central Processing Unit (CPU) 110, retrieving data in the required form from the data store. 120. Output information resulting from performance of a method incorporating the present invention may be restored in data storage 120, or sent to an input/output (I/O) interface circuit 140, which may include a network interface to send and receive data to and from other network nodes. The CPU 110 and its associated data store 120 and program store 130 may be collectively referred to as a “processing circuit.” It will be appreciated that variations of this processing circuit are possible, including circuits that include one or more of several types of programmable circuit elements, e.g., microprocessors, microcontrollers, digital signal processors, field-programmable application-specific integrated circuits, and the like. as well as processing circuits in which all or part of the processing functionality described herein is performed using dedicated digital logic.

[00104] In this way, in various embodiments of the invention, processing circuits, such as the CPU 110, data storage 120 and program storage 130 of Figure 14, are configured to perform one or more of the techniques described in detail previously. Of course, it will be noticed that not all steps of these techniques are necessarily carried out on a single microprocessor or even on a single module.

[00105] It will also be appreciated that all of the details and variations discussed previously in connection with the signal flowcharts of Figures 9 and 10 and the process flowcharts of Figures 11-13 may apply to various embodiments of the example nodes illustrated in Figure 14 .

[00106] It will further be appreciated that various aspects described above can be understood as being carried out by functional “modules”, which can be program instructions that execute on an appropriate processor circuit, digital circuit system and/or analog circuit system with coding. 15 illustrates an example base station 200, for example, which is configured for operation in a wireless communications network and to facilitate wireless synchronization with a neighboring base station. 200, which may have a physical configuration such as that of Figure 7 and/or Figure 14, includes a determination module 210 for determining that a first neighboring cell of a plurality of neighboring cells is interfering with, or is likely to interfere with, a signal from the second neighboring cell, which is used for synchronization. The base station 200 further includes a sending module 220 for sending, in the direction of the first neighboring cell and in response to said determination, a request for activation of a mute pattern of the reference signal by the first neighboring cell. The various variations described above in connection with the process flow chart of Figure 11 are particularly applicable to the base station 200, which may comprise additional modules, such as an additional determination module for determining that the first neighboring cell is no longer required for synchronization and a additional sending module for sending a message indicating that the reference signal squelch pattern can be disabled to the second neighboring cell.

[00107] Similarly, Figure 16 illustrates another representation of a base station 300, which is also configured for operation in a wireless communications network and to facilitate wireless synchronization between neighboring base stations. The base station includes a receive module 310 for receiving a request for activation of a reference signal muting pattern for a cell supported by the base station, and further includes an activation module 320 for activating the reference signal muting pattern. in response to the request. The various variations described above in connection with the process flow chart of Figure 12 are particularly applicable to the base station 300, which may comprise additional modules, such as an additional receive module, for receiving a request to disable the reference signal mute pattern. and a deactivation module for deactivating the reference signal muting pattern in response to the request.

[00108] Figure 17 illustrates a representation of a control node 400, which is also configured for operation in a wireless communications network and to facilitate wireless synchronization between neighboring base stations. The control node 400 comprises a receiving module 410 for receiving a first message from the first base station, the first message indicating that silencing of the reference signal by at least one second neighboring cell of the plurality of neighboring cells is necessary, and a sending module 420 for sending a second message to at least one second base station corresponding to the second neighboring cell, the second message requesting the activation of a reference signal mute pattern for the second neighboring cell. The various variations described above in connection with the process flow chart of Figure 13 are particularly applicable to the control node 400.

[00109] Still additional embodiments of the currently described techniques and apparatus include computer program products comprising program instructions that, when executed by an appropriate processing circuit in a base station, control node or the like, cause the node to perform one or more of the methods described above. In some embodiments, any one or more of these computer program products may be embodied in a computer-readable medium, including a non-transitory medium, such as a memory, writable disk, or other storage device.

[00110] Examples of various embodiments of the present techniques have been described in detail previously, in relation to the attached illustrations of specific embodiments, and are summarized in a listing below. Because it is certainly not possible to describe every conceivable combination of components or techniques, those skilled in the art realize that the present invention can be implemented in ways different from those specifically presented here, without departing from the essential characteristics of the invention. The illustrative embodiments discussed more generally above should therefore be considered, in all respects, as illustrative and not restrictive.

Claims (33)

1. Method, at a base station operating in a wireless communications network, for facilitating wireless synchronization with a neighboring base station, characterized in that the method comprises: receiving synchronization information from a second neighboring cell, the synchronization information indicating at least one of a stratum level and a synchronization state, and evaluating the received synchronization information; determining (1120) that a first neighboring cell of a plurality of neighboring cells is interfering with, or is likely to interfere with, a signal from the second neighboring cell, which is used for synchronization; and sending (1130) in the direction of the first neighboring cell, in response to said determination, a request for activation of a reference signal silencing pattern by the first neighboring cell. 2. Method according to claim 1, characterized by the fact that it further comprises subsequently determining (1140) that the signal from the second neighboring cell is not necessary or unavailable for synchronization and, in response, sending (1150) a message, in the direction of the first neighboring cell, which indicates that the reference signal muting pattern can be deactivated. 3. The method of claim 1 or 2, wherein the request for activation is sent to a control node in the wireless communications network, wherein the control node controls a base station corresponding to the first neighboring cell . 4. Method according to claim 1 or 2, characterized in that the request for activation is sent to a base station corresponding to the first neighboring cell. 5. Method according to any one of claims 1 to 4, characterized by the fact that it further comprises determining (1110) that the second neighboring cell is a source of desired synchronization, before determining that the first neighboring cell is interfering with, or is likely to interfere with the second neighboring cell, based, at least in part, on a signal strength of a signal received from the second neighboring cell. 6. Method according to any one of claims 1 to 5, characterized by the fact that it further comprises receiving an indication whether a reference signal silencing pattern is available for the first neighboring cell before sending the request, wherein said sending the request is responsive to the receipt of said indication. 7. Method according to claim 6, characterized by the fact that the indication comprises or is associated with an identification of one or more silencing patterns available for the first neighboring cell. 8. Method according to any one of claims 1 to 7, characterized in that the request for activation of the reference signal silencing pattern includes a list of cells to which a silencing pattern is to be applied. 9. Method according to any one of claims 1 to 8, characterized in that the request for activation of the reference signal silencing pattern includes an identification of one or more resources that are to be silenced. 10. The method of claim 9, wherein identifying one or more resources to be silenced comprises a subframe pattern, or a pattern periodicity, or both. 11. Method according to any one of claims 1 and 3 to 10, characterized by the fact that it additionally comprises performing synchronization based on the signal coming from the second neighboring cell. 12. Method according to any one of claims 1 to 11, characterized by the fact that it further comprises receiving information that identifies which resources are being silenced or are to be silenced by the first neighboring cell. 13. Method, in a first base station operating in a wireless communications network, for facilitating wireless synchronization by a neighboring base station, characterized by the fact that the method comprises: receiving a request for synchronization information and responding with synchronization information including at least an indication that one or more reference signal squelch patterns is/are available; receiving (1210) a request for activation of a reference signal muting pattern for a cell supported by the base station; and activating (1220) the reference signal muting pattern in response to the request. 14. The method of claim 13, further comprising subsequently receiving (1230) a request to deactivate the reference signal muting pattern and, in response, deactivating (1240) the reference signal muting pattern. reference. 15. The method of claim 14, wherein the synchronization information comprises an identification of one or more features that are muted in at least one first muting pattern of the reference signal. 16. The method of claim 15, wherein identifying one or more features that are silenced comprises a subframe pattern, or a pattern periodicity, or both. 17. Method according to any one of claims 13 to 16, characterized in that the request for activation is received from another base station through a base station to base station interface. 18. The method of any one of claims 13 to 16, wherein the request for activation is received from a control node in the wireless communications network. 19. Base station (100, 200) configured to operate in a wireless communications network and to facilitate wireless synchronization with a neighboring base station, characterized by the fact that the base station (100, 200) is adapted to: receive synchronization information from a second neighboring cell, the synchronization information indicating at least one of a stratum level and a synchronization state, and evaluating the received synchronization information; determining that a first neighboring cell of a plurality of neighboring cells is interfering with, or is likely to interfere with, a signal from the second neighboring cell, which is used for synchronization; and sending in the direction of the first neighboring cell, in response to said determination, a request for activation of a reference signal silencing pattern by the first neighboring cell. 20. Base station (100, 200) according to claim 19, characterized in that the base station (100, 200) is further adapted to subsequently determine that the signal originating from the second neighboring cell is not needed or is unavailable for synchronization and, in response, send a message, in the direction of the first neighboring cell, which indicates that the reference signal silencing pattern can be deactivated. 21. Base station (100, 200) according to claim 19 or 20, characterized in that the base station (100, 200) is further adapted to determine that the second neighboring cell is a desired synchronization source, before determining that the first neighboring cell is interfering with, or is likely to interfere with, the second neighboring cell, based, at least in part, on a signal strength of a signal received from the second neighboring cell. 22. Base station (100, 200) according to any one of claims 19 to 21, characterized in that the base station (100, 200) is further adapted to receive an indication whether a reference signal silencing pattern is available to the first neighboring cell prior to sending the request, wherein sending the request is responsive to the receipt of said indication. 23. Base station (100, 200) according to claim 22, characterized in that the indication comprises or is associated with an identification of one or more silencing patterns available for the first neighboring cell. 24. Base station (100, 200) according to any one of claims 19 to 23, characterized in that the request for activation of the reference signal silencing pattern includes a list of cells in which a silencing pattern is to be applied. 25. Base station (100, 200) according to any one of claims 19 to 24, characterized in that the request for activation of the reference signal silencing pattern includes an identification of one or more resources that are to be silenced. 26. Base station (100, 200) according to claim 25, characterized in that the identification of one or more resources that are to be silenced comprises a subframe pattern, or a pattern periodicity, or both. 27. Base station (100, 200) according to any one of claims 19 to 26, characterized in that the base station (100, 200) is additionally adapted to perform synchronization based on the signal coming from the second neighboring cell. 28. Base station (100, 200) according to any one of claims 19 to 27, characterized by the fact that the base station (100, 200) is further adapted to receive information that identifies which resources are being silenced or should be silenced by the first neighboring cell. 29. First base station (100, 300) configured to operate in a wireless communications network and to facilitate wireless synchronization by a neighboring base station, characterized by the fact that the first base station (100, 300) is adapted to : receiving a request for synchronization information and responding with synchronization information that includes at least an indication that one or more reference signal muting patterns is/are available; receiving a request to activate a reference signal muting pattern for a cell supported by the base station; and activating the reference signal muting pattern in response to the request. 30. The first base station (100, 300) of claim 29, wherein the base station is further adapted to subsequently receive a request to disable the reference signal mute pattern and, in response, disable the reference signal muting pattern. 31. The first base station (100, 300) of claim 29, wherein the synchronization information comprises an identification of one or more resources that are muted in at least one first mute pattern of the reference signal. 32. The first base station (100, 300) of claim 31, wherein the identification of one or more resources that are muted comprises a subframe pattern, or a pattern periodicity, or both. 33. Computer-readable storage medium, characterized in that it contains, stored therein, computer-readable instructions that, when read by a processor, cause the computer to perform the method as defined in any one of claims 1 to 18 .