WO2015160296A1

WO2015160296A1 - Methods and base stations for energy savings in a home base station

Info

Publication number: WO2015160296A1
Application number: PCT/SE2014/050475
Authority: WO
Inventors: Johan Rune; Badawi YAMINE; Oumer Teyeb
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2014-04-17
Filing date: 2014-04-17
Publication date: 2015-10-22

Abstract

An idea of this disclosure is to let a first base station, e.g. a home base station, enter (320) a sleep mode when there is no UE using the first base station (i.e. within a cell controlled by the first base station) and when there is no UE in the proximity of the cell controlled by the first base station. Otherwise, when one or several UEs are either using the first base station or when one or several UEs are in the proximity of the cell controlled by the first base station regular operation is maintained (350), or continued. By allowing for the switching to a sleep mode in periods of no or little utilization of the resources in the radio cell controlled by the first base station it is made possible to save energy.

Description

METHODS AND BASE STATIONS FOR ENERGY SAVINGS

IN A HOME BASE STATION

TECHNICAL FIELD

The present disclosure relates to methods and base stations for energy saving.

BACKGROUND

In third generation (3G) Universal Mobile Telecommunications Systems (UMTS) and in particular in its evolved version System Architecture Evolution/Long Term Evolution (SAE/LTE), also referred to as Evolved Packet System (EPS), the concept of home base stations is introduced. In 3G, a home base station is referred to as a Home Node B (HNB) whereas in EPS it is referred to as a Home eNodeB (HeNB) and the abbreviation HN is used to denote either a 3G Home Node B or an EPS/LTE Home eNodeB. A cell served by a HNB or a HeNB is sometimes referred to as a femtocell. A home base station is assumed to be placed in a private home, utilizing the fixed broadband connection of the home owner to access the core network. It is also assumed that the home owner handles the actual physical installation of the home base station. Generally, the deployment of home base stations cannot be planned, since it is largely outside the control of the operator. Another important characteristic of the home base station concept is the potentially very large number of home base stations.

A HN generally connects to the operator's network via a secure tunnel (supposedly IPsec protected) to a security gateway at the border of the operator's network. Via this tunnel the HN connects to the core network nodes of the operator's core network. The 3GPP operator may also deploy a concentrator node in its core network between the HNs and the regular core network nodes. (3GPP (3^rd Generation Partnership Project) is a standardization body which specifies the standards for 3G/UMTS and EPS/SAE/LTE. A 3GPP operator is an operator which operates a telecommunication system implementing one or more of the 3GPP standards.) In the EPS standardization such a concentrator node is commonly referred to as a HeNB Gateway, which may be an optional node in EPS HeNB solutions. The corresponding node name in 3G UMTS standardization is HNB Gateway and this node is generally mandatory in 3G HNB systems. In this specification both HNB Gateways and HeNB Gateways may also be referred to as HN Gateways. For both EPS and 3G UMTS the HN uses a broadband access network (e.g. Digital Subscriber Line technology (xDSL), Cable) as part of the transport network. Through this setup a mobile terminal, also known as user equipment (UE), may communicate via the HN and the core network like any other UE. HNs have several advantages for both the users and the operators:

For the user. The user will generally receive good indoor coverage which is reflected in high call quality. The user will enjoy high throughput as the capacity of the HN is shared only by few subscribers. Furthermore, less User Equipment (UE) battery energy is consumed as compared with the case when the UE communicates with a macro cell, the main reason being that the UE does not have to overcome home walls propagation in this case. Also, the user can get additional benefits like lower charging rates (e.g. "free" or "pre-paid" if the user has a flat rate subscription to the fixed broadband connection) For the operator: Generally, when an operator wants to have a good indoor coverage, it needs to install more macro cell base station which is rather costly (both in money and time) as each macro cell site needs planning, configuration, etc. Also, the installation of many macros in a dense populated area might generate additional radio interference, especially in the downlink. Instead, excellent indoor coverage can be assured by deploying a multitude of HNs, which are cheap when compared to macros and less prone to interfere with each other due to their limited transmission powers. Lower deployment and operation costs can then enable the operator to attract/provide services to more subscribers.

The HN concept is closely related to the concept of Closed Subscriber Group (CSG). A femtocell is also assumed to be a CSG cell. This means that only a selected group of subscribers are allowed to access the network through that cell. The CSG of a CSG cell is identified by a CSG ID, which is broadcast in the cell as a part of the system information (SI). Typically, each CSG cell has its own unique CSG ID but it is also possible to define the same CSG ID for multiple cells, thereby forming a CSG zone, in which the same selected group of subscribers is allowed access. Although a CSG cell in principle does not have to be a femtocell, the two terms are sometimes used as synonyms.

Hence, all subscribers are not allowed to access a certain HN and a certain subscriber is not allowed to access all HNs. Under supervision of the operator the owner of a HN (or the administrator of the CSG(s) associated with the cell(s) served by the HN) defines which subscribers are allowed to access a femtocell (CSG cell) of the HN (i.e. which subscribers that are included in the CSG of the femtocell). This is assumedly done through a web interface (or other "interface" between the HN owner and the operator), and the CSG data (or HN access list (which is an equivalent term assuming that the HN only serves one CSG)) is stored in a database in the operator's network. The HN owner would assumedly enter the allowed subscribers in the form of ISDN (Integrated Services Digital Network) numbers (MSISDN, Mobile Subscriber ISDN Number) or IMSIs (International Mobile Subscriber Identities) of the concerned subscribers.

The search for allowed CSG cells is not governed by the network, but is left to the UE to handle autonomously. In order to identify an allowed CSG cell, the UE must read the CSG ID from the system information broadcast in the cell and compare it with the CSG ID(s) stored in a list referred to as "CSG Whitelist" or "Allowed CSG List". When a match is found the UE has discovered an allowed CSG cell. To make the search for an allowed CSG cell more efficient the UE is assumed to utilize a so-called "fingerprint" of the CSG cell location. The exact mechanisms of such a fingerprint aided cell search are not standardized and will be up to each UE vendor to design. However, e.g. a fingerprint is obtained by listening to transmissions from the macrocells (i.e. regular cells which typically are much larger than femtocells) in the area of the allowed CSG cell. Transmissions from both LTE cells, 3G cells and 2G cells may be utilized to form a "signature'V'fingerprint" of the location of the CSG cell. Transmitted data that may be useful indications include e.g. cell identities (E-CGI (Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) Cell Global Identity) in EPS and CGI (Cell Global Identity) in 2G/3G), registration area identifiers, such as Tracking Area Identities (TAIs) in EPS, Location Area Identities (LAIs) and Routing Area Identities (RAIs) in 2G/3G and UTRAN Registration Area (URA) identities in 3G. Other types of radio transmissions could potentially also be used to provide input data to the fingerprint, e.g. Wireless Local Area Network (WLAN) or Worldwide Interoperability for Microwave Access (WMAX) transmissions. The UE learns the fingerprint (i.e. records relevant received data which can be used to identify the location) of a CSG cell when it is present in the cell. Later, when searching for the CSG cell (or before searching for the CSG cell) the UE scans the radio environment and when it receives an indication of a fingerprint match (i.e. sufficiently many of the pieces of data constituting the fingerprint match the received ones), the UE determines that it is worthwhile to check the CSG ID of detected potential CSG cells. Also the network may be aware of the fingerprint, e.g. the network may know in which macro tracking area (i.e. a tracking area comprising macrocells) a UE has an allowed CSG cell. The network may have learnt this when the UE accessed the network using a CSG cell.

A general trend in the telecommunication business is that, e.g. as a result of rising energy prices, the energy consumed by the network equipment represents an increasingly large part of the cost of operating the network. Together with the global environmental trend and the increasing importance for enterprises to have good environmental images, this has caused operators to demand that vendors of infrastructure equipment come up with ways to reduce the energy consumption of the telecommunication equipment. In an attempt to provide for energy saving, WO2010/151 186 A1 has presented a home base station in one of its embodiments. The home base station disclosed in

WO2010/151186 A1 detects if no UE allowed to access the home base station is located in the vicinity of the home base station. If no UE is detected by the home base station, the home base station enters a sleep mode. The sleep mode is maintained by the home base station until an indication is received by the home base station. Thus, when there is no UE using the home base station the home base station can enter a sleep mode and the home base station can "wake up" from this sleep mode when there is/are one or more UEs in the vicinity which is/are allowed to access the home base station. While WO 2010/151 186 A1 provides many advantages, there is still a need for further improvements with respect to energy saving. SUMMARY

It is in view of these considerations and others that the various embodiments disclosed herein have been made. A general object addressed by the appended independent claims is therefore to provide for further improvements with respect to energy saving. Further advantageous embodiments are defined in the appended dependent claims.

In one of its aspects, the technology presented herein concerns a method performed by a first base station for saving energy of the first base station. The first base station is communicatively connected to at least one neighboring second base station. It is detected whether there exist UEs allowed to access the first base station in the vicinity of the first base station. This method step, or action, comprises receiving a message from the at least one neighboring second base station. This message comprises information indicating whether there exist UEs allowed to access the first base station in the vicinity of the first base station. In response to detecting that there is no UE allowed to access the first base station in the vicinity of the first base station, a sleep mode is entered. Otherwise, in response to detecting that there is at least one UE allowed to access the first base station, regular operation is continued. The sleep mode is a mode during which the first base station performs radio transmissions less frequently than during regular operation. Furthermore, the sleep mode is maintained until an indication to switch to regular operation is received. This method step, or action, comprises maintaining the sleep mode until a message from the at least one second base station is received. This latter message comprises information indicating that there exists at least one UE allowed to access the first base station in the vicinity of the first base station.

Optionally, the method may additionally comprise receiving a message from the at least one neighboring second base station, wherein this message comprises information indicating that there exists no UE allowed to access the first base station in the vicinity of the first base station. In response to receiving this message comprising the information indicating that there exist no UE allowed to access the first base station in the vicinity of the first base station, the operation in the sleep mode is continued.

Advantageously, but not necessarily, the first base station may be a home base station and the second base station may be a macro base station. In another of its aspects, the technology presented herein concerns a first base station configured to perform, or otherwise execute, the above-mentioned method. The first base station may be a home base station, such as a HNB or a HeNB.

In yet another of its aspects, the technology presented herein concerns a method performed by a second base station for assisting a neighboring first base station in saving energy of the first base station. The second base station is communicatively connected to the neighboring first base station. It is detected whether there exist UEs allowed to access the first base station in a radio cell controlled by the second base station. In response to detecting that there exists at least one UE allowed to access the first base station in the radio cell controlled by the second base station, it is determined, or otherwise concluded, that the at least one UE allowed to access the first base station is in the vicinity of a radio cell controlled by the first base station. Furthermore, in response to determining that the at least one UE allowed to access the first base station is in the vicinity of the radio cell controlled by the first base station a message is transmitted to the first base station. This message comprises information indicating that there exists at least one UE allowed to access the first base station in the vicinity of the first base station.

The total number of UEs allowed to access the first base station that are in the radio cell controlled by the second base station may be counted, e.g. by means of a counter of the second base station. Additionally, the counted total number of UEs allowed to access the first base station may be stored, e.g. in a storage such as a memory of the second base station. By counting the total number of UEs allowed to access the first base station that is in the radio cell controlled by the second base station it is made possible for the second bases station to keep track of the number of UEs that can potentially access the first home base station. The action, or method step, of detecting whether there exist UEs allowed to access the first base station in the radio cell controlled by the second base station may comprise the following method steps, or actions: each time a UE is handed over to the second base station from a neighboring base station determining whether said UE is a UE allowed to access the first base station; in response to determining that said UE is a UE allowed to access the first base station furthermore determining that the UE is in vicinity of the first base station; and in response to determining that the UE is in vicinity of the first base station updating the stored counted total number of UEs allowed to access the first base station by incrementing, i.e. counting up, the total number of UEs allowed to access the first base station.

Additionally, or alternatively, the action, or method step, of detecting whether there exist UEs allowed to access the first base station in the radio cell controlled by the second base station may comprise the following method steps, or actions: each time a UE allowed to access the first base station is handed over from the second base station to a neighboring base station updating the stored counted total number of UEs allowed to access the first base station by decrementing, i.e. counting down, the total number of UEs allowed to access the first base station. Advantageously, but not necessarily, the first base station may be a home base station and the second base station may be a macro base station.

In still another of its aspects, the technology presented herein concerns a second base station configured to perform the above-mentioned method. The second base station may be a macro base station, such as a NB or an eNB.

In yet another of its aspects, the technology presented herein concerns a system comprising the above-mentioned first home base station and one or several above- mentioned second home base stations.

An advantage with embodiments described herein is that the energy consumption of the first base station may be limited, or reduced. The first base station and one or more neighboring second base stations may co-operate to detect whether there is/are no, one or several UE(s) allowed to access the first base station in the vicinity, or proximity, of the first home base station. When there is no UE allowed to access the first base station in the vicinity of the first base station, a sleep mode is entered. Otherwise, when there is at least one UE allowed to access the first base station in the vicinity of the first base station, the first base station can switch to (or stay in) regular operation. Thus, during periods when no UE is using or no UE is approaching the radio cell controlled by the first base station, the first base station can enter the sleep period and thus save energy. Consequently, energy is not consumed unnecessarily much. It is an advantage that neighboring second base station(s) assist(s) the first base station in detecting UEs allowed to access the first base station in the vicinity of the first home base station. This way, not only those UEs detectable by the first base station itself are considered but also those UEs that are detectable by the neighboring second base stations in the radio cells controlled by the second base stations. In other words, also UEs that are potentially approaching the radio cell controlled by the first base station are counted for. This in turn may have the positive effect that the switching between sleep mode and regular mode (or, regular operation), and vice versa, can be made quickly.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages will be apparent and elucidated from the following description of various embodiments, reference being made to the accompanying drawings, in which:

Figs. 1 and 2 illustrate a cellular telecommunication network wherein embodiments disclosed herein may be employed: Figs. 3A-3C illustrate flowcharts of an example method performed by a first base station, such as a home base station;

Fig. 4 illustrates a flowchart of an example method performed by a second base station, such as a macro base station;

Figs. 5-7 show different embodiments of a first base station, herein exemplified by a home base station configured to control a CSG cell;

Figs. 8-10 show different embodiments of a second base station, herein exemplified by a macro base station configured to control macro radio cell(s);

Fig. 11 shows an example embodiment in the form of a computer program; and

Fig. 12 shows an example embodiment in the form of a computer program. DETAILED DESCRIPTION

The technology will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments are shown. The technology may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the technology to those persons skilled in the art. Like reference numbers refer to like elements or method steps throughout the description. In the appended claims, the terms first base station and second base station are used in a non-limiting manner. In a typical example scenario which will be detailed herein, the first base station is a home base station (e.g. a HNB or HeNB) and the second base station is a macro base station (e.g. a NB or eNB). As previously mentioned, the access to a radio cell served by a home base station is typically restricted to a limited group of subscribers, i.e. a Closed Subscriber Group (CSG). Therefore, a radio cell controlled, or served, by a home base station may sometimes be referred to as a CSG cell throughout this disclosure. In some embodiments, the home base station may utilize a "hybrid mode", which means that any UE may access its radio cell but a limited group of subscribers (or UEs associated with said subscribers, to be more specific) are prioritized. This prioritization may come in many different forms. One way of prioritizing is e.g. that the prioritized UEs are given prioritized access when the resources in the CSG are limited, whereas the other UEs are allowed access only when there are superfluous resources available in the cell. However, in other scenarios the first base station may be a so-called low-power node (LPN), which generally serves a smaller radio cell than macro base stations. In such scenarios, the second base station may be a macro base station (e.g. a NB or eNB) which serves a comparatively larger radio cell. The macro base station is sometimes called high-power nodes (HPN) in such scenarios. A LPN generally serves its radio cell(s) without restricted access. In view of this, even if the disclosure will hereinafter focus on the above-mentioned typical scenario where the first base station is a home base station and the second base station is a macro base station, those skilled in the art will understand that the disclosed embodiments are not limited in scope to this typical scenario.

The embodiments disclosed herein may be implemented in a cellular telecommunication network as exemplified in FIG 1 and FIG 2. In the example scenario in FIG. 1 and FIG. 2, the second base stations, i.e. macro base stations, 104 provide cell coverage for UEs 108. In addition, a first base station 102, exemplified by a home base station, which only a limited group of users is allowed to access, is provided. The home base station 102 is serving a UE 108x. The home base station 102 may be connected to the macro base stations via an optional gateway 106 and/or via an optional Mobility Management Entity (MME) (not shown). Alternatively, the home base station 102 may be connected directly to the macro base stations, e.g. via an X2 interface or a similar interface. In the following, while many of the various embodiments may be described mainly with respect to EPS/LTE terminology, it will come to mind to one skilled in the art having benefit of the teachings presented herein and associated drawings that the general principles and concepts described herein can equally possible be utilized in e.g. UMTS/WCDMA/HSPA.

An idea of the technology disclosed herein is to let the home base station 102 enter a sleep mode, when there is no UE using the home base station 102 and/or when there is no UE in the proximity of the radio cell(s) controlled by the home base station 102, i.e. the CSG cell(s). The sleep mode is a mode during which the home base station 102 e.g. performs radio transmissions less frequently than during regular operation. Thus, the sleep mode can be seen as a low-power mode where the home base station 102 consumes less power than during regular operation (i.e. when the home base station 102 is in its 'regular operation'-mode). Also, the home base station 102 may return to regular operation as soon as there is at least one UE allowed to access the home base station 102 either in the CSG cell controlled by the home base station 102 or when there is at least one UE allowed to access the home base station 102 in a radio cell that is controlled by a neighboring macro base station 104 (which thus means that the at least one UE is in proximity to the CSG cell). More particularly, the home base station 102 and the one or several neighboring macro base stations 104 may cooperate to keep track of the total number of UEs allowed to access the home base station 102 that are currently present in the CSG cell as well as in the neighboring macro cells that are surrounding (thus, in sufficient proximity of) the CSG cell. The home base station 102 may thus determine, or otherwise decide, when to enter sleep mode and when to return to (or stay in) regular operation depending on the

presence/absence of UEs allowed to access home base station 102 in the CSG cell or in the surroundings of the CSG cell. Or said differently, the home base station 102 may determine when to turn on or turn off the CSG cell depending on the presence/absence of UEs allowed to access home base station 102 in the CSG cell and in the

surroundings of the CSG cell. An advantage is therefore that that the energy

consumption of the home base station 102 may be limited, or reduced.

Turning now to FIG. 3A, an embodiment of a method performed by, or otherwise executed in, a first base station 102 will be described. In the following, the first base station will be exemplified as a home base station 102, e.g. a HNB or a HeNB. The home base station 102 is configured to serve UEs allowed to access the home base station 102 in the CSG cell controlled by the home base station 102. Also, in the following the second base stations 104 will be exemplified as macro base stations 104, such as a NB or eNB. The macro base stations 104 are configured to serve UEs in their respective radio cell(s) controlled by the respective macro base stations 104. As can be seen in FIGs 1 and 2, the home base station 102 is communicatively connected to at least one, i.e. one or several, neighboring second base stations 104.

Action 310

The home base station 102 detects whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station 102. More particularly, the home base station 102 itself may detect if there exist UEs allowed to access the home base station in the vicinity, i.e. proximity, of the home base station 102. In other words, the home base station 102 may determine whether there exist UEs allowed to access the home base station 102 within the coverage area of the home base station 102, i.e. within the CSG cell. Action 320

If, or when, it is detected in action 310 that there is no UE allowed to access the first base station 102 in the vicinity of the home base station 102 (cf. "NO" in FIG. 3A), the home base station 102 enters a sleep mode. The sleep mode is a mode during which the home base station 102 performs radio transmissions less frequently than during regular operation (i.e. during its "regular operation" mode). Thus, the sleep mode can be seen as a low-power mode during which the home base station 102 consumes less power compared to when the home base station 102 operates in its "regular operation" mode.

Action 330

The sleep mode is maintained until an indication to switch to regular operation (i.e. "regular operation" mode) is received.

Action 340

If, or when, an indication to switch to regular operation (i.e. "regular operation" mode) is received, the home base station 102 leaves the sleep mode. Thus, the home base station 102 may return to regular operation. In other words, upon receiving said indication the home base station 102 may return to the regular operation mode.

Action 350

If, or when, it is detected in action 310 that there is at least one UE (i.e. one or more UEs) allowed to access the home base station 102 in the vicinity of the home base station 102 (cf. "YES" in FIG. 3A), the home base station 102 selects regular operation mode. Thus, in response to detecting that there is at least one UE allowed to access the home base station 102 regular operation is continued, or maintained.

With reference to FIG. 3B, further details with respect to action, or method step, 310 of FIG. 3A will be described.

Action 311

The action 310 of detecting whether there exist UEs allowed to access the home base station comprises receiving a message from the at least one neighboring macro base station 104. The message comprises information indicating whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station 102. For example, the message may comprise one or more data field(s) including, or otherwise indicating, said information indicating whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station 102.

As will be appreciated, a message may be received wherein said message comprises information indicating that there is no UE allowed to access the home base station 102 in the vicinity of the home base station 102. Alternatively, a message may be received wherein said message comprises information indicating that there is at least one UE (i.e. one, two or more UEs) allowed to access the home base station 102 in the vicinity of the home base station 102.

With reference to FIG. 3C, further details with respect to actions, or method steps, 330 and 340 of FIG. 3A will now be described.

Action 331

The action 330 of maintaining the sleep mode until an indication to switch to regular operation is received comprises maintaining the sleep mode until receiving a message from the at least one second base station 104, wherein said message comprises information indicating that there exists at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102. For example, the message may comprise one or more data field(s) including, or otherwise indicating, said information indicating that there exists at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102.

Action 341

If, or when, a message comprising information indicating that there is at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102 ("cf. "YES" in FIG. 3C) is received, then the home base station 102 leaves the sleep mode. Thus, the home base station 102 may return to regular operation. In other words, upon receiving said message from the macro base station 104 the home base station 102 may return to the regular operation mode.

Otherwise, and in response to receiving a message (from a macro base station 104) comprising information indicating that there exists no UE allowed to access the home base station 102 in the vicinity of the home base station 102 (cf. "NO" in FIG. 3C), the home base station 102 may continue its operation in the sleep mode. Thus, the sleep mode may be maintained.

Turning now to FIG. 4, an embodiment of a method performed by, or otherwise executed in, a second base station 104 will be described. Similar to above, the second base station will be exemplified as a macro base station 104, e.g. a NB or an eNB. The macro base station 104 is configured to serve UEs in the radio cell(s) controlled by the macro base station 104. Also similar to the above, the first base station 102 will be exemplified as a home base station such as a HNB or a HeNB. As can be seen in FIGs 1 and 2, the macro base station 104 is communicatively connected to neighboring home base station 102.

Action 410

The macro base station 104 detects whether there exist UEs allowed to access the home base station 102 in the radio cell(s) controlled by the macro base station 102. The radio cell(s) controlled by the macro base station 102 are sometimes called macro radio cells or macro cells.

Whether or not an UE is a UE allowed to access the home base station 102 may be determined in various ways as will be appreciated by those skilled in the art.. As a mere example, this information (sometimes called "CSG membership information") may become available to the macro base station when a UE is being handed over to the macro cell or when the UE transitions from idle mode to connected mode in the macro cell. For example, this information may become available along with UE context information from a MME.

Action 420

In response to detecting that there exists at least one UE allowed to access the home base station 102 in the radio cell(s) controlled by the macro base station 104 it is determined, or otherwise concluded or assumed, that said at least one UE allowed to access the home base station 102 is in the vicinity of the CSG cell controlled by the home base station 102. This is based the notion that the CSG cell controlled by the home base station 102 is neighboring the radio cell(s) controlled by the macro base station(s) 104 that is/are neighboring the home base station 102. Since the radio cells(s) controlled by the macro base station(s) 104 is/are thus located in proximity to the CSG cell a UE served in a radio cell of a macro base station 104 will be concluded to be in the vicinity, i.e. sufficient proximity, of the home base station 102. Action 430

In response to determining that said at least one UE allowed to access the home base station 102 is in the vicinity of the radio cell controlled by the home base station (i.e. the CSG cell), a message is transmitted to the home base station 102, wherein said message comprises information indicating that there exists at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102, i.e. in proximity to the CSG cell controlled by the home base station 102.

Action 440

The macro base station 104 may optionally count the total number of UEs allowed to access the home base station 102 that are in the radio cell(s) controlled by the macro base station 104. For example, the macro base station 104 may comprise a counter or counter functionality to count the total number of UEs allowed to access the home base station 102 that are in the radio cell(s) controlled by the macro base station 104. As will be appreciated by those skilled in the art, the counter or counter functionality may be realized by hardware or software or a combination thereof.

Action 450

Preferably, but not necessarily, the macro base station 104 stores the counted total number of UEs allowed to access the home base station 102. For example, the counted total number of UEs allowed to access the home base station 102 may be stored in a storage, such as in one or more memories.

Action 460

If, or when, it is detected in action 410 that there is no UE allowed to access the home base station 102 in the radio cell(s) controlled by the macro base station 104, the macro base station 104 may optionally transmit a message to the home base station 102, wherein said message comprises information indicating that there exists no UEs allowed to access the home base station 102 in the radio cell(s) controlled by the macro base station 104. The home base station 102 may thus be informed that there is no UE allowed to access the home base station 102 in the vicinity of the home base station 102. It should be appreciated that this optional action 460 may preferably be performed, or executed, only for the first time when the counted total number of UEs allowed to access the home base station 102 becomes zero. In other words, if the counted total number of UEs continues to be zero at subsequent actions 410, it is not necessary to transmit this message more times.

In the following, further optional details with respect to action 410 will be described. In some embodiments, the action 410 of detecting whether there exist UEs allowed to access the home base station in the radio cell(s) controlled by the macro base station 104 comprises the following actions, or method steps:

each time a UE is handed over to the macro base station 104 from a neighboring base station (e.g. from a home base station or from another macro base station), it is determined whether said UE is a UE allowed to access the home base station.

If, or when, it is determined that said UE is a UE allowed to access the home base station 102 it is furthermore determined, or concluded, that the UE is in vicinity of the home base station 102. This determination, or conclusion, is based the notion that the CSG cell controlled by the home base station 102 is neighboring the radio cell(s) controlled by the macro base station(s) 104 that is/are neighboring the home base station 102. Since the radio cells(s) controlled by the macro base station(s) 104 is/are thus located in proximity to the CSG cell a UE served in a radio cell of a macro base station 104 will be concluded to be in the vicinity, i.e. sufficient proximity, of the home base station 102.

If, or when, it is determined that the UE is in vicinity of the home base station 102, the stored counted total number of UEs allowed to access the home base station 102 may be updated by incrementing, i.e. counting up, the total number of UEs allowed to access the home base station 102.

Additionally, or alternatively, the action 410 of detecting whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station 102 may comprise the following action, or method step:

each time a UE allowed to access the home base station 102 is handed over from the macro base station 104 to a neighboring base station (e.g. a home base station or another macro base station) the stored counted total number of UEs allowed to access the home base station 102 may be updated by decrementing, i.e. counting down, the total number of UEs allowed to access the home base station 102. With reference to FIG. 5 an embodiment of a first base station 102 will be described. The first base station 102 is configured to perform the method described hereinabove with respect to FIG 3. The first base station 102 is exemplified by a home base station, such as HNB or a HeNB. The home base station 102 is communicatively connectable to at least one neighboring second base station 104, such as a NB or an eNB. In the example embodiment of FIG. 5, the home base station 102 comprises means 510 adapted to detect whether there exist UEs allowed to access the home base station 102 in the vicinity of the first base station. The home base station 102 also comprises means 520 adapted to enter the home base station 102 in a sleep mode in response to detecting that there is no UE allowed to access the first base station 102 in the vicinity of the home base station 102. Again, the sleep mode is a mode during which the home base station 102 performs radio transmissions less frequently than during regular operation. Additionally, the home base station 102 comprises means 530 adapted to maintain the sleep mode until an indication to switch to regular operation is received by the home base station 102. Still further, the home base station 102 comprises means 540 adapted to continue regular operation of the home base station 102 in response to detecting that there is at least one UE allowed to access the home base station 102. Still further, the home base station 102 comprises means 511 adapted to receive a message from the at least one neighboring macro base station 104, wherein said message comprises information indicating whether there exist UEs allowed to access the first base station 102 in the vicinity of the home base station 102. Also, the home base station 102 comprises means 531 adapted to maintain the sleep mode until a message from the at least one macro base station 104 is received, wherein said message comprises information indicating that there exists at least one UE (i.e. one or several UEs) allowed to access the home base station 102 in the vicinity of the home base station 102. The home base station 102 may also comprise means 51 1 adapted to receive a message from the at least one neighboring macro base station 104, wherein said message comprises information indicating that there exists no UEs allowed to access the home base station 102 in the vicinity of the home base station 102. Also, the home base station 102 may comprise means 531 adapted to continue operation in the sleep mode in response to receiving said message comprising said information indicating that there exists no UEs allowed to access the home base station 102 in the vicinity of the home base station 102. With reference to FIG. 6, an alternative embodiment of a first base station 102, here exemplified by a home base station, will be briefly described. The home base station 102 may comprise a communications interface 610, a processor 620 and a memory 630. The communications interface 610 may comprise a transmitter (Tx) and a receiver (Rx). Alternatively, the communications interface 610 may comprise a transceiver (Tx/Rx).

The memory 630 stores computer program code, which, when run in the processor 620 causes the home base station 102 to: detect whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station 102; in response to detecting that there is no UE allowed to access the home base station 102 in the vicinity of the home base station 102 enter a sleep mode; otherwise in response to detecting that there is at least one UE allowed to access the home base station 102 continue regular operation. The memory 630 also stores computer program code, which, when run in the processor 620 causes the home base station 102 to receive, by means of the receiver (Rx) a message from the at least one neighboring macro base station 104, wherein said message comprises information indicating whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station 102.

Moreover, the memory 630 also stores computer program code, which, when run in the processor 620 causes the home base station 102 to maintain the sleep mode until the receiver (Rx) receives a message from the at least one macro base station, wherein said message comprises information indicating that there exists at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102.

Optionally, the memory 630 may store computer program code, which, when run in the processor 620 causes the home base station 102 to receive, by means of the receiver (Rx), a message from the at least one neighboring macro base station, wherein said message comprises information indicating that there exists no UEs allowed to access the home base station 102 in the vicinity of the home base station 102. The memory 630 may also store computer program code, which, when run in the processor 620 causes the home base station 102 to: continue operation in the sleep mode in response to the receiver (Rx) receiving said message comprising said information indicating that there exists no UEs allowed to access the first base station in the vicinity of the first base station. With reference to FIG. 7, an alternative embodiment of a first base station (e.g. a home base station 102) will be briefly described. The home base station 102 may comprise a processor 710, various modules 720, a transmitter (Tx) 730 and a receiver (Rx) 740. The transmitter 730 and the receiver 740 may alternatively be implemented as a transceiver (Tx/Rx). More particularly, the home base station 102 comprises a UE detection module 721 for detecting whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station 102. A sleep mode module 722 is also provided. In response to detecting by the UE detection module 721 that there is no UE allowed to access the home base station 102 in the vicinity of the home base station 102 the sleep mode module 722 is configured to enter the home base station 102 in a sleep mode. Otherwise, a regular operation module 723 is configured to continue regular operation if the UE determination module 721 has determined that there is at least one UE allowed to access the home base station 102.

Furthermore, the receiver 740 is configured to receive a message from at least one neighboring macro base station, wherein said message comprises information indicating whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station 102. In one embodiment, the sleep mode module 722 is configured to maintain the sleep mode until the receiver 740 receives a message from the at least one macro base station 104, wherein said message comprises information indicating that there exists at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102.

Optionally, the receiver 740 may be configured to receive a message from the at least one neighboring macro base station 104, wherein said message comprises information indicating that there exists no UE allowed to access the home base station 102 in the vicinity of the home base station 102. The regular operation module 723 may be configured to continue regular operation in response to the receiver 740 receiving said message comprising said information indicating that there exists no UEs allowed to access the home base station 102 in the vicinity of the home base station 102.

Turning now to FIG. 8, an embodiment of a second base station 104 will be described. The second base station 104 is configured to perform the method described hereinabove with respect to FIG 4. The second base station 102 is exemplified by a macro base station, such as NB or an eNB. The macro base station 104 is communicatively connectable to a neighboring first base station 102, such as home base station (e.g. a HNB or a HeNB). In the example embodiment of FIG. 8, the macro base station 104 comprises means 810 adapted to detect whether there exist UEs allowed to access the home base station 102 in a radio cell controlled by the macro base station 104. The macro base station 104 also comprises means 820 adapted to determine that at least one UE allowed to access the home base station is in the vicinity of a radio cell controlled by the home base station 102 in response to detecting that there exists at least one UE allowed to access the home base station 102 in the radio cell controlled by the macro base station 104. Moreover, the macro base station comprises means 830 adapted to transmit a message to the home base station 102 in response to determining that said at least one UE allowed to access the home base station 102 is in the vicinity of the radio cell controlled by the home base station 102, wherein said message comprises information indicating that there exists at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102.

The macro base station 104 may optionally comprise means 840 adapted to count the total number of UEs allowed to access the home base station 102 that are in the vicinity of the home base station 102, and means 850 adapted to store the counted total number of UEs allowed to access the first base station 102.

In some embodiments, the means denoted 810 is further adapted to: each time a UE is handed over to the macro base station 104 from a neighboring base station (e.g. a home base station or another macro base station) determine whether said UE is a UE allowed to access the home base station 102; in response to determining that said UE is a UE allowed to access the home base station 102 furthermore determine that the UE is in vicinity of the home base station 102; and in response to determining that the UE is in vicinity of the home base station 102 update the stored counted total number of UEs allowed to access the home base station 102 by counting up the total number of UEs allowed to access the home base station 102. Additionally, or alternatively, the means denoted 810 may be further adapted to: each time a UE allowed to access the home base station 102 is handed over from the macro base station 104 to a neighboring base station (e.g. a home base station or another macro base station) update the stored counted total number of UEs allowed to access the home base station 102 by counting down the total number of UEs allowed to access the home base station 102.

Furthermore, the macro base station 104 may comprise means 830 adapted to transmit a message to the home base station 102 in response to detecting that there is no UE allowed to access the home base station 102 in the vicinity of the home base station 102, wherein said message comprises information indicating that there exists no UEs allowed to access the home base station 102 in the vicinity of the home base station 102.

With reference to FIG. 9, an alternative embodiment of a second base station 104, here exemplified by a macro base station, will be briefly described. The macro base station 104 may comprise a communications interface 910, a processor 920 and a memory 930. The communications interface 910 may comprise a transmitter (Tx) and a receiver (Rx). Alternatively, the communications interface 910 may comprise a transceiver (Tx/Rx).

The memory 930 stores computer program code, which, when run in the processor 920 causes the macro base station 104 to: detect whether there exist UEs allowed to access the home base station 102 in a radio cell controlled by the macro base station 104; in response to detecting that there exists at least one UE allowed to access the home base station 102 in the radio cell controlled by the macro base station 104 also determine that said at least one UE allowed to access the home base station 102 is in the vicinity of a radio cell controlled by the home base station 102; and in response to determining that said at least one UE allowed to access the home base station 102 is in the vicinity of the radio cell controlled by the home base station also transmit (i.e. send), by means of the transmitter a message to the home base station 102, wherein said message comprises information indicating that there exists at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102.

The memory 930 may also store computer program code, which, when run in the processor 920 causes the macro base station 104 to count the total number of UEs allowed to access the home base station 102 that are in the radio cell controlled by the macro base station 104. The counted total number of UEs allowed to access the home base station 102 may be stored e.g. in memory 930, or in another memory (not shown) internal of or associated with the macro base station 104. The memory 930 may also store computer program code, which, when run in the processor 920 causes the macro base station 104 to: each time a UE is handed over to the macro base station from a neighboring base station determine whether said UE is a UE allowed to access the home base station 102; in response to determining that said UE is a UE allowed to access the home base station 102 furthermore determine that the UE is in vicinity of the home base station 102; and in response to determining that the UE is in vicinity of the home base station 102 update the stored counted total number of UEs allowed to access the home base station 102 by counting up the total number of UEs allowed to access the home base station 102. The memory 930 may additionally, or alternatively, store computer program code, which, when run in the processor 920 causes the macro base station 104 to: each time a UE allowed to access the home base station 104 is handed over from the macro base station 104 to a neighboring base station (e.g. the home base station 102 or another macro base station 104) update the stored counted total number of UEs allowed to access the home base station 102 by counting down the total number of UEs allowed to access the home base station 102.

The transmitter 910 may be configured to transmit a message to the first base station, wherein said message comprises information indicating that there exists no UEs allowed to access the first base station in the vicinity of the first base station in response to detecting that there is no UE allowed to access the home base station 102 in the radio cell controlled by the macro base station 104. With reference to FIG. 10, an alternative embodiment of a second base station (e.g. a macro base station 104) will be briefly described. The macro base station 104 may comprise a processor 1010, various modules 1020, a transmitter (Tx) 1030 and a receiver (Rx) 1040. The transmitter 1030 and the receiver 1040 may alternatively be implemented as a transceiver (Tx/Rx). More particularly, the macro base station 104 UE detection module 1021 for detecting whether there exist UEs allowed to access the home base station 102 in a radio cell controlled by the macro base station 104. A CSG cell vicinity determination module 1022 is also provided. The CSG cell vicinity determination module 1022 is configured to determine that said at least one UE allowed to access the home base station 102 is in the vicinity of a radio cell controlled by the home base station 102 in response to the UE detection module 1021 detecting that there exists at least one UE allowed to access the home base station 102 in the radio cell controlled by the macro base station 104. Furthermore, the transmitter 1030 is configured to transmit a message to the home base station 102, wherein said message comprises information indicating that there exists at least one UE allowed to access the home base station 102 in the vicinity of the home base station 102.

The macro base station may optionally comprise a counter module 1023. The counter module 1023 may be configured to count the total number of UEs allowed to access the home base station 102 that are in the radio cell(s) controlled by the macro base station 104. Also, the macro base station 104 may comprise a storage 1050, e.g. in the form of one or more memories, for storing the counted total number of UEs allowed to access the home base station 102.

In some embodiments, the UE detection module denoted 1021 is configured to: each time a UE is handed over to the macro base station 104 from a neighboring base station (e.g. a home base station or another macro base station 104) determine whether said UE is a UE allowed to access the home base station 102; in response to determining that said UE is a UE allowed to access the home base station 102 furthermore determine that the UE is in vicinity of the home base station 102; and in response to determining that the UE is in vicinity of the home base station update the stored counted total number of UEs allowed to access the home base station 102 by counting up the total number of UEs allowed to access the home base station 102. Additionally, or alternatively, the UE detection module 1021 is configured to: each time a UE allowed to access the first base station is handed over from the macro base station 104 to a neighboring base station (e.g. a home base station or another macro base station 104) update the stored counted total number of UEs allowed to access the home base station 102 by counting down the total number of UEs allowed to access the home base station 102.

In some embodiments, the transmitter 1030 may additionally be configured to transmit a message to the first base station, wherein said message comprises information indicating that there exists no UEs allowed to access the first base station in the vicinity of the home base station 102.

Turning now to FIG. 11 , yet another embodiment is disclosed. Fig. 11 illustrates a computer program comprising instructions which, when executed on at least one processor 1130 of a first base station 11 10, will cause the first base station 1110 to: detect whether there exist UEs allowed to access the first base station in the vicinity of the first base station; in response to detecting that there is no UE allowed to access the first base station in the vicinity of the first base station, enter a sleep mode, which is a mode during which the first base station performs radio transmissions less frequently than during regular operation, and maintain the sleep mode until an indication to switch to regular operation is received; otherwise in response to detecting that there is at least one UE allowed to access the first base station continuing regular operation. Detecting whether there exist UEs allowed to access the first base station may further comprise receiving by a receiver (not shown) a message from at least one neighboring second base station, wherein said message comprises information indicating whether there exist UEs allowed to access the first base station in the vicinity of the first base station. Also, maintaining the sleep mode until an indication to switch to regular operation is received may comprise comprises maintaining the sleep mode until receiving a message, by the receiver (not shown), from the at least one second base station, wherein said message comprises information indicating that there exists at least one UE allowed to access the first base station in the vicinity of the first base station. A carrier may comprise the above-mentioned computer program. The carrier may be a computer readable storage medium 1 100. Alternatively, the carrier may be one of an electronic signal, an optical signal, or a radio signal. In some embodiments, the first base station may be embodied as a home base station 102.

Turning now to FIG. 12, yet another embodiment is disclosed. Fig. 12 illustrates a computer program comprising instructions which, when executed on at least one processor 1230 of a second base station 1210, will cause the second base station 1210 to: detect whether there exist UEs allowed to access the first base station in a radio cell controlled by the second base station; in response to detecting that there exists at least one UE allowed to access the first base station in the radio cell controlled by the second base station determine that said at least one UE allowed to access the first base station is in the vicinity of a radio cell controlled by the first base station; and in response to determining that said at least one UE allowed to access the first base station is in the vicinity of the radio cell controlled by the first base station also transmit a message to the first base station, wherein said message comprises information indicating that there exists at least one UE allowed to access the first base station in the vicinity of the first base station. A carrier may comprise the above-mentioned computer program. The carrier may be a computer readable storage medium 1200. Alternatively, the carrier may be one of an electronic signal, an optical signal, or a radio signal. In some embodiments, the second base station may be embodied as a macro base station 104. It should be appreciated that when discussing UEs in the embodiments described herein, the UEs may include UEs in IDLE mode and/or a UEs in CONNECTED mode. In other words, when detecting whether there exist UEs allowed to access the home base station 102 in the vicinity of the home base station, IDLE mode UEs and/or CONNECTED mode UEs may be considered. For example, methods and techniques as described in WO 2013/051988 A1 and WO2010/151 186 A1 , respectively, may be utilized in connection with various aspects of the embodiments disclosed herein.

An advantage with embodiments described herein is that the energy consumption of the first base station may be limited, or reduced. The first base station and one or more neighboring second base stations may co-operate to detect whether there is/are no, one or several UEs allowed to access the first base station in the vicinity, or proximity, of the first home base station. When there is no UE allowed to access the first base station in the vicinity of the first base station, a sleep mode is entered. Otherwise, when there is at least one UE allowed to access the first base station in the vicinity of the first base station, the first base station can switch to (or stay in) regular operation. Thus, during periods when no UE is using or when no UE is approaching the radio cell controlled by the first base station (i.e. the CSG cell), the first base station can enter the sleep period and thus save energy. Consequently, energy is not consumed unnecessarily much. It is an advantage that neighboring second base station(s) assist(s) the first base station in detecting UEs allowed to access the first base station in the vicinity of the first home base station. This way, not only those UEs detectable by the first base station itself are considered but also those UEs that are detectable by the neighboring second base stations in the radio cells controlled by the second base stations. In other words, also UEs that are potentially approaching the radio cell controlled by the first base station are counted for. This in turn may have the positive effect that the switching between sleep mode and regular mode (or, regular operation) can be made more quickly. In the detailed description hereinabove, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of various embodiments described in this disclosure. In some instances, detailed descriptions of well-known devices, components, circuits, and methods have been omitted so as not to obscure the description of the embodiments disclosed herein with unnecessary detail. All statements herein reciting principles, aspects, and embodiments disclosed herein, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. Thus, for example, it will be appreciated that block diagrams herein can represent conceptual views of illustrative circuitry or other functional units embodying the principles of the embodiments. Similarly, it will be appreciated that any flow charts and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. The functions of the various elements including functional blocks, may be provided through the use of hardware such as circuit hardware and/or hardware capable of executing software in the form of coded instructions stored on computer readable medium. Thus, such functions and illustrated functional blocks are to be understood as being either hardware-implemented and/or computer-implemented, and thus machine-implemented. In terms of hardware implementation, the functional blocks may include or encompass, without limitation, digital signal processor (DSP) hardware, reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) [ASIC], and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions. In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers. When provided by a computer or 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 may be shared or distributed. Moreover, use of the term "processor" or "controller" shall also be construed to refer to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

Modifications and other variants of the described embodiments will come to mind to one skilled in the art having benefit of the teachings presented in the foregoing description and associated drawings. Therefore, it is to be understood that the embodiments are not limited to the specific example embodiments disclosed and that modifications and other variants are intended to be included within the scope of this disclosure. Furthermore, although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Therefore, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the appended claims. As used herein, the terms "comprise/comprises" or "include/includes" do not exclude the presence of other elements or steps. Furthermore, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion of different claims does not imply that a combination of features is not feasible and/or advantageous. Also, it should be noted that in the description of embodiments, the partition of functional blocks into particular units is by no means limiting. Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. In the same manner, functional blocks that are described herein as being implemented as two or more units may be implemented as a single unit without departing from the scope of the claims. In addition, singular references do not exclude a plurality. Finally, reference signs in the claims are provided merely as a clarifying example and should not be construed as limiting the scope of the claims in any way.

Claims

A method (300) performed by a first base station for saving energy of the first base station, which first base station is communicatively connected to at least one neighboring second base station, the method comprising:

detecting (310) whether there exist User Equipments, UEs, allowed to access the first base station in the vicinity of the first base station;

in response to detecting that there is no UE allowed to access the first base station in the vicinity of the first base station, entering (320) a sleep mode, which is a mode during which the first base station performs radio transmissions less frequently than during regular operation, and maintaining (330) the sleep mode until an indication to switch to regular operation is received; otherwise

in response to detecting that there is at least one UE allowed to access the first base station continuing (350) regular operation,

the method being characterized in that said detecting (310) whether there exist UEs allowed to access the first base station further comprises receiving (311) a message from the at least one neighboring second base station, wherein said message comprises information indicating whether there exist UEs allowed to access the first base station in the vicinity of the first base station; and in that said maintaining (330) the sleep mode until an indication to switch to regular operation is received comprises maintaining (331) the sleep mode until receiving a message from the at least one second base station, wherein said message comprises information indicating that there exists at least one UE allowed to access the first base station in the vicinity of the first base station.

The method (300) according to claim 1 , comprising receiving (311) a message from the at least one neighboring second base station, wherein said message comprises information indicating that there exists no UE allowed to access the first base station in the vicinity of the first base station; and in response to receiving said message comprising said information indicating that there exists no UE allowed to access the first base station in the vicinity of the first base station continuing (331) operation in the sleep mode.

3. The method according to claim 1 or 2, wherein the first base station is a home base station and wherein the second base station is a macro base station.

A method (400) performed by a second base station for assisting a neighboring first base station in saving energy of the first base station, which second base station is communicatively connected to the neighboring first base station, the method comprising:

detecting (410) whether there exist User Equipments, UEs, allowed to access the first base station in a radio cell controlled by the second base station;

in response to detecting that there exists at least one UE allowed to access the first base station in the radio cell controlled by the second base station determining (420) that said at least one UE allowed to access the first base station is in the vicinity of a radio cell controlled by the first base station; and

in response to determining (420) that said at least one UE allowed to access the first base station is in the vicinity of the radio cell controlled by the first base station transmitting (430) a message to the first base station, wherein said message comprises information indicating that there exists at least one UE allowed to access the first base station in the vicinity of the first base station.

The method according to claim 4, comprising:

counting (440) the total number of UEs allowed to access the first base station that are in the radio cell controlled by the second base station; and

storing (450) the counted total number of UEs allowed to access the first base station.

The method according to claim 4 or 5, wherein detecting (410) whether there exist UEs allowed to access the first base station in the radio cell controlled by the second base station comprises:

each time a UE is handed over to the second base station from a neighboring base station determining whether said UE is a UE allowed to access the first base station; in response to determining that said UE is a UE allowed to access the first base station furthermore determining that the UE is in vicinity of the first base station; and

in response to determining that the UE is in vicinity of the first base station updating a stored counted total number of UEs allowed to access the first base station by incrementing the total number of UEs allowed to access the first base station.

The method according to claim 4, 5 or 6, wherein detecting (410) whether there exist UEs allowed to access the first base station in the vicinity of the first base station comprises:

each time a UE allowed to access the first base station is handed over from the second base station to a neighboring base station updating the stored counted total number of UEs allowed to access the first base station by decrementing the total number of UEs allowed to access the first base station.

The method according to any one of the claims 4-7, comprising, in response to detecting that there is no UE allowed to access the first base station in the radio cell controlled by the second base station:

transmitting (460) a message to the first base station, wherein said message comprises information indicating that there exists no UE allowed to access the first base station in the vicinity of the first base station.

The method according to any one of claims 4-8, wherein the first base station is a home base station and wherein the second base station is a macro base station.

10. A first base station (102) for saving energy of the first base station (102), which first base station (102) is communicatively connectable to at least one neighboring second base station (104) , the first base station (102) comprising: means (510) adapted to detect whether there exist User Equipments, UEs, allowed to access the first base station (102) in the vicinity of the first base station; means (520) adapted to enter the first base station (102) in a sleep mode in response to detecting that there is no UE allowed to access the first base station (102) in the vicinity of the first base station, wherein the sleep mode is a mode during which the first base station (102) performs radio transmissions less frequently than during regular operation,

means (530) adapted to maintain the sleep mode until an indication to switch to regular operation is received by the first base station (102); and

means (540) adapted to continue regular operation of the first base station (102) in response to detecting that there is at least one UE allowed to access the first base station (102),

the first base station (102) being characterized in that it comprises means (511) adapted to receive a message from the at least one neighboring second base station (104), wherein said message comprises information indicating whether there exist UEs allowed to access the first base station (102) in the vicinity of the first base station (102); and in that it comprises means (531) adapted to maintain the sleep mode until a message from the at least one second base station (104) is received, wherein said message comprises information indicating that there exists at least one UE allowed to access the first base station (102) in the vicinity of the first base station (102).

11. The first base station (102) according to claim 10, comprising:

means (51 1) adapted to receive a message from the at least one neighboring second base station (104), wherein said message comprises information indicating that there exists no UE allowed to access the first base station (102) in the vicinity of the first base station (102); and

means (531) adapted to continue operation in the sleep mode in response to receiving said message comprising said information indicating that there exists no UE allowed to access the first base station (102) in the vicinity of the first base station (102).

12. The first base station (102) according to claim 10 or 1 1 , wherein the first base station is a home base station.

13. A second base station (104) for assisting a neighboring first base station (102) in saving energy of the first base station (102), which second base station (104) is communicatively connectable to the neighboring first base station (102), the second base station (104) comprising:

means (810) adapted to detect whether there exist User Equipments,

UEs, allowed to access the first base station (102) in a radio cell controlled by the second base station (104);

means (820) adapted to determine that at least one UE allowed to access the first base station is in the vicinity of a radio cell controlled by the first base station (102) in response to detecting that there exists at least one UE allowed to access the first base station (102) in the radio cell controlled by the second base station (104); and

means (830) adapted to transmit a message to the first base station (102) in response to determining that said at least one UE allowed to access the first base station is in the vicinity of the radio cell controlled by the first base station

(102), wherein said message comprises information indicating that there exists at least one UE allowed to access the first base station (102) in the vicinity of the first base station (102). 14. The second base station (104) according to claim 13, comprising:

means (840) adapted to count the total number of UEs allowed to access the first base station (102) that are in the vicinity of the first base station (102); and

means (850) adapted to store the counted total number of UEs allowed to access the first base station (102).

15. The second base station (104) according to claim 13 or 14, wherein the means (810) adapted to detect whether there exist UEs allowed to access the first base station (102) in the radio cell controlled by the second base station (104) is further adapted to:

each time a UE is handed over to the second base station (104) from a neighboring base station determine whether said UE is a UE allowed to access the first base station (102); in response to determining that said UE is a UE allowed to access the first base station furthermore determine that the UE is in vicinity of the first base station (102); and

in response to determining that the UE is in vicinity of the first base station (102) update the stored counted total number of UEs allowed to access the first base station (102) by incrementing the total number of UEs allowed to access the first base station (102).

16. The second base station (104) according to claim 13, 14 or 15, wherein the means (810) adapted to detect whether there exist UEs allowed to access the first base station (102) in the radio cell controlled by the second base station (104) is further adapted to:

each time a UE allowed to access the first base station is handed over from the second base station (104) to a neighboring base station update the stored counted total number of UEs allowed to access the first base station

(102) by decrementing the total number of UEs allowed to access the first base station (102).

17. The second base station (104) according to any one of the claims 13-16, comprising means (830) adapted to transmit a message to the first base station in response to detecting that there is no UE allowed to access the first base station in the vicinity of the first base station, wherein said message comprises information indicating that there exists no UEs allowed to access the first base station in the vicinity of the first base station.

18. The second base station (104) according to any one of the claims 13-17, wherein the second base station is a macro base station.

19. A system comprising a first base station (102) according to any of the claims 10-12 and at least one second base station (104) according to any one of the claims 13-18.