Closed subscriber group (CSG) handling for supporting network sharing of home base stations

A system and method for enhanced support for handling of Closed Subscriber Groups (CSGs) and sharing of Radio Access Network (RAN) for home base stations and other small cells. An enhanced System Information (SI) structure indicates multiple CSG IDs and CSG Indications, thereby making it possible to support different CSG IDs and CSG Indications for every Public Land Mobile Network Identity (PLMN-ID) and also to support a PLMN-ID with multiple associated CSG IDs and CSG Indications. The enhanced SI makes it possible to have different CSG IDs for different operators, to have multiple CSG IDs for one operator (i.e., a single PLMN), and to selectively use the CSG concept for some PLMNs (as given by their respective CSG Indications), but not for all. A network of base stations (e.g., a RAN) thus can be effectively shared by multiple operators, leading to better cellular coverage, peak rates, and capacity.

Not Applicable

Not Applicable

BACKGROUND

The present invention relates to sharing of home base stations in wireless networks. More particularly, and not by way of limitation, the present invention is directed to a system and method to support sharing of home base stations among multiple cellular networks via enhanced handling of Closed Subscriber Group (CSG) related information in System Information (SI).

The usage of mobile broadband services using cellular networks has shown a significant increase during recent years. In parallel to this, there is an ongoing evolution of Third Generation (3G) and Fourth Generation (4G) cellular networks like High Speed Packet Access (HSPA), Long Term Evolution (LTE), Worldwide Interoperability for Microwave Access (WiMAX), etc., to support ever-increasing performance with regards to capacity, peak bit rates and coverage. Operators deploying these networks are faced with a number of challenges, e.g., related to site costs and availability, transport costs and availability, lack of wireless spectrum, etc. Many different techniques are considered for meeting these challenges and providing cost-efficient mobile broadband.

One option available to the operators is to use shared network infrastructure and sites, especially when multiple cellular operators agree to deploy their network together. This is beneficial since it reduces the total deployment costs, and can provide benefits due to pooling of the available spectrum. One drawback with network sharing in its current form is that it requires quite a lot of cooperation between the operators sharing the network. Because the network configuration is common for a part of the network that is shared, it may make it difficult to differentiate the treatment of users from each operator. The sharing of a part of the network may also make interaction (e.g., handover) with non-shared part more complex, since the shared part needs to interact with multiple non-shared networks (managed by multiple operators).

The support for network sharing has been enhanced in the Third Generation Partnership Project's (3GPP) Universal Terrestrial Radio Access Network (UTRAN) and Evolved UTRAN (E-UTRAN) standards and is defined in, for instance, 3GPP's Technical Specifications (TS) 23.251, 23.401 and 36.300 (these and other specifications may be obtained at ftp://ftp.3gpp.org/Specs/latest). The UTRAN and E-UTRAN standards allow different scenarios for network sharing, but it is expected that a common scenario will be when the Radio Access Network (RAN) is shared and each operator has its own Core Network (CN). This scenario, which is called Multi-Operator Core Network (MOCN) in 3GPP, is illustrated inFIG. 1. In the MOCN configuration ofFIG. 1, an operator X's RAN10is shared by operator-specific Core Networks12-14from three different operators—operator A, operator B, and operator C. In an MOCN configuration, multiple CN nodes (e.g., nodes12-14) may be connected to the same Radio Network Controller (RNC) (not shown) in the shared RAN (e.g., RAN10inFIG. 1), even when these CN nodes are operated by different network operators. It is observed here that MOCN is a network-sharing configuration in which only the RAN is shared, as opposed to Gateway Core Network (GWCN)—a network-sharing configuration in which parts of the operator core networks are also shared.

From a technical point of view, the MOCN configuration uses the multi-to-multi connectivity of the UTRAN's Iu (as described, for example, in 3GPP TS 25.413) and E-UTRAN's S1 (as described, for example, in 3GPP TS 36.413) interfaces between the RAN and CN as exemplarily illustrated by the dotted line16inFIG. 1. The MOCN configuration thus makes it possible to connect a RAN node (e.g., an RNC or an Evolved Node-B (eNB or eNodeB) (not shown inFIG. 1)) to multiple CN nodes (e.g., Serving GPRS Support Node (SGSN) wherein “GPRS” refers to General Packet Radio Service, Mobility Management Entity (MME), etc.) belonging to different operators. The RAN will, in this configuration, broadcast one Public Land Mobile Network (PLMN) identity (ID) for each operator sharing the RAN (as described, for example, in TS 25.331 and TS 36.331). As is known, a PLMN is a wireless communication system (e.g., a cellular telephone network) operated by a network operator and intended for use by terrestrial subscribers in vehicles or on foot. In response to RAN's broadcast of PLMN IDs, the User Equipment (UE) or mobile handset will, at initial attach, select which PLMN it wants to connect to, and the RAN will make sure that the initial attach signaling is routed to the correct operator's CN (as described, for example, in TS 23.401 and 23.060). Once the UE has been assigned a CN node, there are also mechanisms making it possible for the RAN and CN to route subsequent signaling related to this UE to the same CN node. Besides the list of PLMN IDs, almost all of the rest of the system information (as described, for example, in TS 25.331 and 36.331) broadcasted on the cell broadcast channel (e.g., the Physical Broadcast Channel (PBCH)) in the shared RAN is common for all operators sharing the RAN. However, currently there are a few exceptions to this common treatment for all operators. For example, in E-UTRAN, the parameter “cellReservedForOperatorUse” is per PLMN (i.e., it is an operator's PLMN-specific). Similarly, in UTRAN, the parameters “Domain Specific Access Restriction Parameters For Operator N” and “Paging Permission with Access Control Parameters For Operator N” are also per PLMN.

Another option available to an operator for network-sharing is the deployment of home base stations (e.g., Home eNB or HeNB (in LTE), Home Node-B or HNB (in HSPA), or a femtocell (as this names is used by www.femtoforum.org)) or other small base stations complementing the traditional macro cellular network. Possible benefits of these small base stations or home base stations are lower site costs due to smaller physical size and lower output power, as well as increased capacity and coverage due to the closer deployment to the end user. The operator can configure the cells with these smaller base stations as Open, Hybrid or Closed. Open cells are possible to use for all subscribers, with no preference to perform cell reselection of individual cells. Closed cells broadcast a Closed Subscriber Group (CSG) cell type (called “CSG Indication” that can either indicate values “true” or “false”) and CSG identity (called “CSG ID” that may be a 27-bit identifier). Closed cells are only available for mobile handsets or UEs belonging to the specific CSG. When the cell is closed, the CSG Indication broadcasted has the value “true”. In addition, users belonging to a CSG have a preference for selecting CSG cells with the same CSG ID. Hybrid cells, on the other hand, may broadcast a CSG ID value, but the CSG Indication broadcasted has the value “false”. Thus, hybrid cells may be available for all users.

Since it is expected that the number of home base stations could be very large and that they are considered less reliable nodes, solutions have been introduced in 3GPP's E-UTRAN and UTRAN standards for home base stations to connect to the CN via a home base station gateway (GW) (e.g., the H(e)NB GW in E-UTRAN or HNB GW in UTRAN). The H(e)NB GW or HNB GW has the functionality to hide the home base station from the rest of the network.

In the LTE/System Architecture Evolution (SAE) case, the HeNB GW is optional and therefore has S1-interfaces on both sides of it.FIG. 2shows an HeNB logical architecture in which an HeNB GW18is shown connected to an HeNB20and a Core Network22via S1 interfaces23and24, respectively. When HeNB GW is implemented, for the rest of the network, the HeNB GW just looks like a large eNB with many cells. From the HeNB point of view, the HeNB GW looks like a CN node (MME). The HeNB may only connect to one HeNB GW and, in this case, the HeNB may not have the network node selection functionality that can allow the HeNB to connect to multiple HeNB GW nodes. Instead, the HeNB GW supports the network node selection functionality enabling support for MME-pools (e.g., from multiple Core Networks). On the other hand, when the HeNB connects directly to the CN (i.e., when HeNB GW is omitted), the HeNB may itself support the network node selection functionality.

In the HSPA/Wideband Code Division Multiple Access (WCDMA) case, the HNB GW is mandatory. A new Iuh-interface is defined between the HNBs and the HNB GW, and the normal Iuh-interface is used between the HNB GW and the CN.FIG. 3depicts an HNB logical diagram in which an HNB GW26is shown connected to an HNB28via an Iuh interface29and to a Core Network30via an Iu interface32. When HNB GW is present, for the rest of the network, the HNB GW just looks like a large RNC with, potentially, many service areas (that is the UTRAN concept for one or multiple cells). The HNB only connects to one HNB GW, and the HNB does not have the network node selection functionality that can allow the HNB to connect to multiple HNB GW nodes. Instead, the HNB GW supports the network node selection functionality enabling support for Mobile Switching Center (MSC)- and SGSN-pools (e.g., from multiple Core Networks).

SUMMARY

As discussed above, although RAN sharing may be available to some extent for home base stations (e.g., HeNBs, HNBs, femtos, etc.), the current 3GPP standard still does not offer good support for RAN sharing for home base stations and other small cells.

One of the problems with the current 3GPP standard is that it is not possible to apply different CSG IDs for the same or different operators. Because of this limitation, the operators would need to coordinate the management of CSG IDs among themselves in case of network-sharing. This coordination also requires interactions with each operator CN because the MME (in a CN) is responsible for determining whether a given UE is allowed to access a given CSG ID. In the single operator case, this current 3GPP limitation means that it is not possible to support partially overlapping CSG areas with different CSG IDs.

Another problem is that it is not possible today in a shared HeNB to operate in Open Access for users belonging to one of the PLMNs and Closed Access for users belonging to another PLMN.

The above-mentioned problems arise because, in the current E-UTRAN implementation, the System Information (SI) from the base station can include up to six (6) different PLMN Identities (PLMN IDs), but can only include a single CSG Indication and a single CSG ID.FIG. 4illustrates various System Information Blocks (SIBs) of an SI40in E-UTRAN. As shown inFIG. 4, the SI40may include a Master Information Block (MIB) followed by different types of SIBs—SIB1(System Information Block type-1), SIB2(System Information Block type-2), etc. As is known, the SIB1may contain information relevant when evaluating if a UE is allowed to access a cell, and may also define the scheduling of other system information blocks. InFIG. 4, the SIB1is shown to include a “cellAccessRelatedInformation” field and other fields (not shown in detail) such as, for example, a “cellSelectionInfo” field, a “frequencyBandIndicator” field, etc. The “cellAccessRelatedInformation” field may include additional fields such as, for example, a “PLMN-Identity List” field, a Tracking Area Code (TAC) field (which is common for all PLMNs listed), a “CellIdentity” (Cell-ID) field, a “CSG Indication” field, a “CSG-ID” field, etc. The six different PLMN IDs (PLMN-ID1through PLMN-ID6) may be provided through the “PLMN-ID List” field, and each PLMN-ID may include a field to convey three (3) decimal digits of Mobile Country Code (MCC) and 2 or 3 decimal digits of Mobile Network Code (MNC), wherein each decimal digit (from 0 through 9) may be represented by up to four binary bits.

There is currently a debate in 3GPP whether HeNBs (in “Hybrid” or “Closed” mode) can be shared among operators (see, for example, the discussion in document numbers G2-100392, R3-103428, R2-106594, R2-106616, and R2-106942 in 3GPP release-9). In the current 3GPP standard, the first listed PLMN-ID (i.e., PLMN-Id1inFIG. 4) identifies the “primary” PLMN to which the cell belongs. RAN2(related to Radio layer2and Radio layer3Radio Resource) agreed in RAN2meeting #72 that the “CSG-ID” in the SIB1only applies to the identity of a CSG within this primary PLMN of the cell. The CSG-ID field is present in a CSG cell, and may be absent if the cell is not a CSG cell. Hence, the UE reports the primary PLMN to the RAN node (e.g., an HeNB) on the source side (see, for example, the discussion in 3GPP rel-9 document number R2-106942). However, currently, at UE registration, the UTRAN HNB GW still must look into the ‘Initial UE message’ to determine the selected Core Network. Furthermore, at handover from one Registered PLMN (RPLMN) (discussed later below) to another PLMN using ‘Inbound Handover’ procedure, it is unclear in current 3GPP standard how the target PLMN is determined.

It is therefore desirable to devise a methodology for enhanced support for RAN-sharing for home base stations and other small cells. The single CSG-ID based approach (as shown inFIG. 4) in current 3GPP may not provide the flexibility needed to offer enhanced network-sharing for home base stations or other small cells.

The present invention provides a solution to the above-mentioned problem of lack of enhanced support in the current 3GPP standard for CSG-handling and network-sharing for home base stations. In one embodiment, the present invention provides different CSG IDs (instead of the single CSG-ID as shown inFIG. 4) for the same or different operators. Different CSG IDs for different operators may reduce requirements for extensive coordination among operators during network-sharing. In case of a single operator, different CSG IDs can be useful when the operator wants to enable CSG-specific access restrictions to some cells (i.e., for some users), but wants to allow other cells to be shared by different CSG IDs (i.e., making them available to more users). Furthermore, selective access to a shared HeNB may be supported through multiple CSG IDs. Such support many be desirable in cases when operators have different service layer agreements with the owner of the HeNB. For instance, if the HeNB operates in one operator spectrum, it might be desirable for this operator to use Open or Hybrid Access, but at the same time offer the possibility to other operator to support Closed Access.

In one embodiment, the present invention is directed to a method of communicating CSG-related information with a UE. Using a processor that is in wireless communication with the UE, the method comprises the steps of: providing SI to the UE containing at least one of the following: a PLMN-specific CSG-ID parameter for each of a plurality of PLMNs identified in the SI, and a PLMN-specific CSG Indication parameter for each of the plurality of PLMNs identified in the SI; and, receiving from the UE an intimation of a PLMN selected by the UE from the plurality of PLMNs identified in the SI.

In another embodiment, the present invention is directed to a method of communicating CSG-related information with a processor that is in wireless communication with a UE. The method comprises: the UE receiving SI from the processor containing at least one of the following: a PLMN-specific CSG-ID parameter for each of a plurality of PLMNs identified in the SI, and a PLMN-specific CSG Indication parameter for each of the plurality of PLMNs identified in the SI; and, the UE sending to the processor an intimation of a PLMN selected by the UE from the plurality of PLMNs identified in the SI.

In a further embodiment, the present invention is directed to a mobile communication node configured to provide a radio interface to a UE. The mobile communication node comprises a processor capable of providing SI to the UE containing at least one of the following: a PLMN-specific CSG-ID parameter for each of a plurality of PLMNs identified in the SI, and a PLMN-specific CSG Indication parameter for each of the plurality of PLMNs identified in the SI. The mobile communication node also comprises a receiver capable of receiving from the UE an intimation of a PLMN selected by the UE from the plurality of PLMNs identified in the SI.

In another embodiment, the present invention is directed to a UE that is wirelessly operable with a mobile communication node via a radio interface provided by the mobile communication node. The UE comprises a receiver capable of receiving SI from the mobile communication node containing at least one of the following: a PLMN-specific CSG-ID parameter for each of a plurality of PLMNs identified in the SI, and a PLMN-specific CSG Indication parameter for each of the plurality of PLMNs identified in the SI. The UE also comprises a processor capable of sending to the mobile communication node an intimation of a PLMN selected by the UE from the plurality of PLMNs identified in the SI.

In another embodiment, the present invention is directed to a system comprising a mobile communication node configured to provide a radio interface to a mobile handset; and the mobile handset wirelessly operable with the mobile communication node via the radio interface provided thereby. The mobile communication node is configured to also provide SI to the mobile handset containing at least one of the following: a PLMN-specific CSG-ID parameter for each of a plurality of PLMNs identified in the SI, and a PLMN-specific CSG Indication parameter for each of the plurality of PLMNs identified in the SI. The mobile handset is configured to send to the mobile communication node an intimation of a PLMN selected by the mobile handset from the plurality of PLMNs identified in the SI.

The present invention thus enables indication of multiple CSG IDs and CSG Indications in the System Information (SI) sent on the cell broadcast channel, thereby making it possible to support different CSG IDs and CSG Indications for every PLMN Identity (PLMN-ID) and also to support a PLMN-ID with multiple associated CSG IDs and CSG Indications. This makes it possible to have different CSG IDs for different operators and even to have multiple CSG IDs for one operator (i.e., a single PLMN). The present invention also makes it possible to selectively use the CSG concept for some PLMNs (as given by their respective CSG Indications), but not for all. The present invention thus improves the possibility to cost-effectively provide enhanced support for RAN-sharing for HeNBs or other base stations using a network's existing radio resources and signaling framework (i.e., without significant disruption to network architecture or functionality). This enhanced support may be useful in opening up new business cases where third party operators deploy a network of base stations (e.g., a RAN) that can be shared by multiple operators, leading to better cellular coverage, peak rates, and capacity.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention. Additionally, it should be understood that although the invention is described primarily in the context of a cellular telephone/data network, the invention can be implemented in other forms of wireless networks as well (for example, a corporate-wide wireless data network, a satellite communication network, and the like).

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” or “according to one embodiment” (or other phrases having similar import) in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Furthermore, depending on the context of discussion herein, a singular term may include its plural forms and a plural term may include its singular form. Similarly, a hyphenated term (e.g., “CSG-ID”) may be occasionally interchangeably used with its non-hyphenated version (e.g., “CSG ID”), and a capitalized entry (e.g., “ID”) may be interchangeably used with its non-capitalized versions (e.g., “id” or “Id”). Such occasional interchangeable uses shall not be considered inconsistent with each other.

It is noted at the outset that the terms “coupled,” “connected”, “connecting,” “electrically connected,” etc., are used interchangeably herein to generally refer to the condition of being electrically connected. Similarly, a first entity is considered to be in “communication” with a second entity (or entities) when the first entity electrically sends and/or receives (whether through wireline or wireless means) information signals (whether containing voice information or non-voice data/control information) to the second entity regardless of the type (analog or digital) of those signals. It is further noted that various figures (including component diagrams) shown and discussed herein are for illustrative purpose only, and are not drawn to scale.

FIG. 5is a diagram of an exemplary wireless system50in which enhanced CSG handling according to the teachings of one embodiment of the present invention may be implemented. The system50may include a mobile handset52that is in wireless communication with a carrier network54of a wireless service provider (or operator) through a communication node56of the carrier network54. The communication node56may be, for example, a base station in a 3G network, or an evolved Node-B (eNodeB) or Home eNodeB (HeNB) when the carrier network is a Long-Term Evolution (LTE) network, or any other home base station or femtocell, and may provide radio interface to the mobile handset52. In other embodiments, the communication node56may also include a site controller, an access point (AP), or any other type of radio interface device capable of operating in a wireless environment. It is noted here that the terms “mobile handset,” “wireless handset,” and “user equipment (UE)” may be used interchangeably herein to refer to a wireless communication device that is capable of voice and/or data communication via a wireless carrier network. Some examples of such mobile handsets include cellular telephones or data transfer equipments (e.g., a Personal Digital Assistant (PDA) or a pager), smartphones (e.g., iPhone™, Android™, Blackberry™, etc.), computers, or any other type of user devices capable of operating in a wireless environment. Similarly, the terms “wireless network” or “carrier network” may be used interchangeably herein to refer to a wireless communication network (e.g., a cellular network) facilitating voice and/or data communication between two user equipments (UE's).

In addition to providing air interface (e.g., as represented by a wireless link57inFIG. 5) to the UE52via an antenna59, the communication node56may also perform radio resource management (as, for example, in case of an eNodeB or HeNB in an LTE system) such as, for example, through transmission of System Information (SI) mentioned hereinbefore. In case of a 3G carrier network54, the communication node56may include functionalities of a 3G base station along with some or all functionalities of a 3G Radio Network Controller (RNC) to perform the enhanced CSG handling through enhanced SI structures discussed below. Communication nodes in other types of carrier networks (e.g., 4G networks and beyond) also may be configured similarly. In one embodiment, the node56may be configured (in hardware, via software, or both) to implement the enhanced CSG handling as discussed herein. For example, when existing hardware architecture of the communication node56cannot be modified, the enhanced CSG handling methodology according to one embodiment of the present invention may be implemented through suitable programming of one or more processors (e.g., processor95(or, more particularly, processing unit99) inFIG. 12) in the communication node56. The execution of the program code (by a processor in the node56) may cause the processor to provide an enhanced SI (for enhanced CSG handling) as discussed herein. Thus, in the discussion below, although the communication node56may be referred to as “performing,” “accomplishing,” or “carrying out” a function or process, it is evident to one skilled in the art that such performance may be technically accomplished in hardware and/or software as desired. Similarly, the UE52may be suitably configured (in hardware and/or software) to perform its portion of PLMN selection, CSG Indication checking, CSG-ID transmission (to the base station or HeNB56), etc., as discussed in more detail below.

It is observed here that, when network-sharing is employed, the communication node56may be part of a Radio Access Network (RAN) (not shown inFIG. 5) in the carrier network54. The RAN may be shared by multiple core networks (not shown) from different operators, thereby requiring the communication node56to provide radio resource management (with/without added RNC functionalities) for enhanced CSG handling as per the teachings of the present invention. The carrier network54may be an operator-specific PLMN. In case of network-sharing, many such PLMNs (not shown) from different operators may share the RAN (not shown) in the carrier network54. For ease of illustration, only one such network configuration50is illustrated inFIG. 5.

The carrier network54may include a core network58coupled to the communication node56and providing logical and control functions (e.g., subscriber account management, billing, subscriber mobility management, etc.) in the network54. In one embodiment, the communication node56may be connected to the core network58via a suitable gateway (e.g., HeNB GW or HNB GW as illustrated inFIGS. 2 and 3, respectively). In case of an LTE carrier network, the core network58may be an Evolved Packet Core (EPC). Regardless of the type of carrier network54, the core network58may function to provide connection of the UE52to other mobile handsets operating in the carrier network54and also to other communication devices (e.g., wireline phones) or resources (e.g., an Internet website) in other voice and/or data networks external to the carrier network54. In that regard, the core network58may be coupled to a packet-switched network60(e.g., an Internet Protocol (IP) network such as the Internet) as well as a circuit-switched network62such as the Public-Switched Telephone Network (PSTN) to accomplish the desired connections beyond the devices operating in the carrier network54. Thus, through the communication node's56connection to the core network58and the handset's52radio link with the communication node56, a user of the handset52may wirelessly (and seamlessly) access many different resources or systems beyond those operating within the carrier network54of an operator.

As is understood, the carrier network54may be a cellular telephone network or a PLMN in which the UE52may be a subscriber unit. However, as mentioned before, the present invention is operable in other non-cellular wireless networks as well (whether voice networks, data networks, or both). Furthermore, portions of the carrier network54may include, independently or in combination, any of the present or future wireline or wireless communication networks such as, for example, the PSTN, or a satellite-based communication link. Similarly, as also mentioned above, the carrier network54may be connected to the Internet via its core network's58connection to the IP (packet-switched) network60or may include a portion of the Internet as part thereof.

As mentioned before, particular embodiments of the present invention enable the indication of multiple CSG IDs and CSG Indications in the system information (e.g., the enhanced SI structure discussed hereinbelow) sent on the cell broadcast channel (e.g., on the Physical Broadcast Channel (PBCH) or on the Physical Downlink Shared Channel (PDSCH) configured to carry a broadcast message), making it possible to support different CSG IDs and CSG Indications for every PLMN Identity (PLMN ID) as well as having PLMN Identities (PLMN IDs) with multiple associated CSG IDs and CSG Indications. This makes it possible to have different CSG IDs for different operators and even have multiple CSG IDs for one operator (PLMN). Furthermore, this enhanced CSG handling according to the teachings of the present invention also makes it possible to use the CSG concept selectively—i.e., for some PLMNs (as given by the CSG indication), but not for all.

FIG. 6is an exemplary depiction of an enhanced SI structure for E-UTRAN according to one embodiment of the present invention. It is noted here that the terms “enhanced SI structure” and “enhanced SI” are used interchangeably herein to essentially refer to the enhanced System Information (discussed with reference toFIGS. 6-9) according to the teachings of the present invention. In the embodiment ofFIG. 6, an enhanced SI structure64enables the indication of different CSG IDs for every PLMN Identity (PLMN-Id) sent in the SI64. As mentioned earlier, up to six (6) different PLMN IDs may be sent through System Information Block type-1(SIB1) in the SI64. Thus, in the SI64inFIG. 6, six different CSG-IDs—collectively referred to by reference numeral “66”—are shown to have been included in the CSG-ID List field of the SIB1. Each CSG-ID66is PLMN-specific—i.e., CSG-Id1applies for PLMN-Id1, CSG-Id2applies for PLMN-Id2, and so on. If there are less than six PLMN IDs in the PLMN-ID List, then the enhanced SI64may contain less than six CSG IDs to maintain one-to-one correspondence with PLMN IDs in the PLMN-ID List. The “CSG Indication” may also be split into several instances, one per PLMN. That is not shown inFIG. 6in order to simplify the drawing, but illustrated in more detail inFIG. 8discussed later hereinbelow.

It is noted that each set of [PLMN ID; CSG ID] may have some associated data. According to current standards, carrier frequencies with only CSG cells need not be broadcasted. For carrier frequencies with mixed CSG and non-CSG cells, SIB4may include a list of PCIs (Physical Cell IDs) allocated to CSG cells and the UE considers this list valid for 24 hours. These data assist the UE in saving battery life by reducing the UE's “autonomous search”. Similar information per PLMN ID may also be provided.

The enhanced SI64may be sent by the HeNB56to the UE52when, for example, enhanced CSG handling is needed to support network-sharing. At other times, the traditional SI40may be used instead. Alternatively, the HeNB56may always send the enhanced SI64regardless of the CSG handling requirements.

It is observed here that although a detailed architecture of internal UE layers is not relevant to the present discussion and is not shown here for the sake of brevity, a brief overview of PLMN selection by a UE is provided in the context of various operational layers in the UE. It is understood that PLMN selection is generally an ongoing process in the upper layers (i.e., the Mobility Management (MM) sub-layer of the Non-Access Stratum layer (NAS)) of a UE (e.g., the UE52inFIG. 5). The initial UE process of choosing the strongest cell (frequency) is known as “camping on a cell”. The Radio Resource Control sub-layer (RRC)/Physical layer (PHY) in a UE find available PLMNs and report them to layers above. Decision of choosing the PLMN may be done by the NAS layer (MM sublayer). MM itself may use PLMN information available in UE's Subscriber Information Module (SIM) to decide which PLMN to select from the available PLMNs reported by RRC/PHY (which may receive a list of available PLMNs through, for example, the PLMN-ID List in the SI from a base station). After the decision from NAS, RRC/PHY may choose the best cell (based on cell selection criteria—e.g., strongest frequency) in PLMN selected by NAS. It is noted here that even though initial cell selection is done, PHY layer may regularly look for a signal-wise “better” cell (radio conditions change as user moves from one place to another). This procedure is known as a “cell re-selection” procedure and is similar to the cell selection procedure briefly discussed herein.

Successful PLMN selection results in that the UE is camping on a so called Registered PLMN (RPLMN), and the UE may also receive a list of equivalent PLMNs (EPLMN) from the PLMN (e.g., the PLMN with which the UE is currently communicating). In one embodiment, an RPLMN may be a cellular service subscriber's Home PLMN (HPLMN). An HPLMN may be a PLMN to which the subscriber belongs (as indicated, e.g., by information stored in UE's SIM card), as opposed to a Visitor PLMN (VPLMN) in which the subscriber is roaming. In another embodiment, RPLMN may be the PLMN that was last-registered by the UE (i.e., to which the UE had successfully attached). Such last-registered PLMN may be stored in UE's memory (e.g., memory94inFIG. 11). The current PLMN may provide an EPLMN list to a UE (e.g., the UE52) identifying all PLMNs that are regarded as “equivalent” to each other (based on their combination of Mobile Country Code (MCC) and Mobile Network Code (MNC)) and that the UE should treat as equivalent for the purpose of PLMN selection, cell selection/re-selection, and handover. This EPLMN list along with an added entry for the PLMN of the current network54may be stored by the UE52in its memory94(FIG. 11), and the list may remain stored in the UE even when UE is switched off so that the list can be used for PLMN selection after switch on. The EPLMN list can be signaled to the UE (e.g., by the network54through the HeNB56) as part of the location area update, routing area update, or GPRS attach procedures, but it could not be possibly signaled on the cell broadcast channel (e.g., PBCH). On the other hand, as mentioned before, the SI may be sent on the cell broadcast channel.

A UE (e.g., the UE52inFIG. 5) may detect that an HeNB is a Shared HeNB (e.g., the HeNB56inFIG. 5)—e.g., by presence of multiple PLMN IDs in the enhanced SI from the HeNB56. When the UE52detects that the HeNB56is a Shared HeNB, the UE52can read the broadcasted PLMN IDs in the SI and select one of these PLMN IDs based on the previous PLMN selection (i.e., only RPLMN or any EPLMN may be selected). The previous PLMN selection may be available from the EPLMN list stored in UE's memory as discussed above. The UE52may then indicate the selected PLMN to the Shared HeNB56as part of the RRC Connection establishment. This intimation from the UE is currently supported by the RRC Connection Request procedure, but not at “inbound mobility to CSG cell”. In one embodiment, as long as there is a single CSG-ID for each PLMN-ID (as shown, for example, inFIG. 6), there may be no need for the UE52to indicate the selected PLMN's CSG-ID separately. Because of one-to-one correspondence between PLMN IDs and CSG IDs in the SI64in the embodiment ofFIG. 6, this means that the PLMN-ID indicated to the Shared HeNB56also indicates the CSG-ID to be used, for example in the signaling between the Shared HeNB56and the MME (in the core network58).

FIG. 7is another exemplary depiction of an enhanced SI structure68for E-UTRAN according to one embodiment of the present invention. In the embodiment ofFIG. 7, the principle of PLMN-specific CSG-ID is further extended by allowing a list of CSG sub-identifiers for one or more of the PLMN IDs in the enhanced SI68. Thus, as shown inFIG. 7, the CSG-ID List may not only include PLMN-specific CSG-ID parameters70(which are similar to the CSG IDs66inFIG. 6), but may also include CSG sub-identifiers for one or more of these CSG IDs (i.e., CSG-Id1through CSG-ID6inFIG. 7). InFIG. 7, the CSG-ID1parameter is shown to constitute CSG sub-identifiers72including CSG-Id1a, CSG-Id1b, etc. Thus, it may be then possible to indicate two or more separate CSG IDs for a single PLMN Id with the use of the concept of CSG sub-identifiers. One example of this is to have CSG Id1aand1bfor the PLMN Id1as shown inFIG. 7. In the embodiment ofFIG. 7, in addition to intimating the selected PLMN to the Shared HeNB56, the UE52may also need to indicate the selected PLMN's CSG sub-identifier(s) in the signaling to the HeNB56. The UE52may select and report one or more of the available CSG sub-identifiers for the CSG-ID ID of the UE-selected PLMN. Although not shown inFIG. 7, it is understood that other PLMN IDs (e.g., PLMN Id2,3, etc.) in the SI68may be similarly provided with corresponding CSG sub-identifiers.

The intimation of selected PLMN and CSG by the UE to the network may occur in different procedures. One procedure is when the UE performs cell reselection to the HeNB cell. In this case the UE informs the target HeNB cell of the selected PLMN and CSG. Another procedure is when the UE performs so-called “inbound handover” towards an HeNB. In the latter case, the UE informs the source HeNB cell about the selected PLMN and CSG.

As mentioned above, it is not possible in the current 3GPP specification that an HeNB broadcasts multiple CSG IDs. Using the current specifications, the HeNB may not support multiple CSG Ds or a single UE may not be a member of more than one of these CSG IDs. The mechanism inFIG. 7to indicate the selected CSG IDs (through CSG sub-identifiers) to the network54could be even further extended so that the HeNB56can broadcast multiple CSG IDs (and corresponding sub-identifiers) and the UE52can select all the allowed CSG IDs and their sub-identifiers (according to an Allowed CSG List (not shown) stored in the UE by, e.g., the operator of UE's HPLMN) and signal them to the network54. The network54(e.g., through an MME in the CN58) may check the UE's access rights to the different CSGs (i.e., the CSGs corresponding to the CSG IDs and sub-identifiers received from the UE) and select one of these CSGs, for example, for the UE52to camp on. The HeNB56may then allow the UE52to access this selected CSG as per UE's access rights.

FIG. 8is an additional exemplary depiction of an enhanced SI structure74for E-UTRAN according to one embodiment of the present invention. The enhanced SI74inFIG. 8enables the indication of different, PLMN-specific CSG Indications76for every PLMN Identity sent in the system information. Thus, in the SI74inFIG. 8, the CSG Indication1(“CSG-Ind1”) applies for PLMN Id1, CSG-Ind2applies for PLMN Id2, and so on. Thus, like the embodiment inFIG. 6, there may be a one-to-one correspondence between a PLMN-ID and a CSG Indication in the embodiment ofFIG. 8.

It is observed here that the exemplary SI structures64and74(inFIGS. 6 and 8, respectively) separately show the extensions to CSG-ID and CSG Indication handling. However, in particular embodiments (e.g., the embodiment inFIG. 9), an enhanced SI structure may utilize these two extensions simultaneously.FIG. 9illustrates an enhanced SI structure78that may be generated when the embodiments inFIGS. 6 and 8are implemented simultaneously. The enhanced SI78may simultaneously indicate multiple PLMN-specific CSG Indications80(as in case ofFIG. 8) and multiple PLMN-specific CSG IDs82(as in case ofFIG. 6) for each of the plurality of PLMNs identified (through the PLMN-ID List) in the SI78. Although not shown inFIG. 9, additional PLMN-specific CSG sub-identifiers (as in case ofFIG. 7) also may be included in the enhanced SI78.

Thus, particular embodiments of the present invention enable the indication of different CSG IDs and CSG Indications for every PLMN Identity sent in the System Information. The indications of multiple allowed CSG IDs (FIG. 6) with/without sub-identifiers (FIG. 7), and/or the indications of multiple CSG Indications (FIGS. 8-9) may be facilitated by adding such indications, for example, in the RRC Connection establishment signaling (e.g., between the HeNB56and the UE52), signaling (e.g., to the core network58) over the S1-MME interface (e.g., as illustrated inFIGS. 1-2), and in the measurement reports for Handover into CSG cells. In one embodiment, the UE52may use a Physical Uplink Control Channel (PUCCH) signal, or (an extended) Physical Random Access Channel (PRACH) signal, or a Physical Uplink Shared Channel (PUSCH) signal to indicate selected CSG IDs (and/or CSG sub-identifiers) and CSG Indications to the HeNB56.

FIG. 10shows an exemplary set of CSG selection actions that may be performed by a UE (e.g., the UE52inFIG. 5) in response to an SIB1message from an HeNB (e.g., the HeNB56inFIG. 5) according to one embodiment of the present invention. By way of example, the UE52may have stored (e.g., in the memory94inFIG. 11) an Allowed CSG List with three different entries as indicated at block84inFIG. 10. This List may have been stored in the UE by the operator of UE's network (e.g., HPLMN or RPLMN) based on UE's users subscription to the network or later by the network (e.g., through RRC signaling) upon UE's initial access to the network. The UE may also receive the Allowed CSG List from an Open Mobile Alliance Device Management (OMA DM) server (as discussed, for example, in TS 24.285). In one embodiment, UE's manufacturer may store such List as well in view of network operator-specific requirements. In one embodiment, the UE may locally amend the List at “Manual CSG Selection”, if the network accepts the location update attempt (as discussed, for example, in TS 24.301). For ease of discussion, only the PLMN-ID and the CSG-ID is shown inFIG. 10for each entry in the UE-based Allowed CSG List. Additional entries (e.g., “HNB Name,” “CSG Type,” a default priority field within each entry, or an indication that a specific entry can only be accessed in emergency situation, etc.) in the List at block84are omitted for the sake of brevity. It is seen from block84that one of the entries in the UE's Allowed CSG List is {PLMN-2, CSG-ID22}.

The Shared HeNB56may broadcast the System Information Block type1(SIB1) message85to the UE52(and also to other UEs (not shown) in the cell) indicating to the UE52that the HeNB56is shared among three different operators (as indicated by the three different PLMN-IDs—PLMN-1, PLMN-2, and PLMN-3—in the SIB1message). HeNB56thus broadcasts information about all these PLMNs through the SIB1message85, which may contain additional information (not shown inFIG. 10for the sake of brevity) similar to the SIB1in the enhanced SI78inFIG. 9. For each PLMN, a separate CSG Indication and CSG-ID are also indicated in the SIB1message as can be seen inFIG. 10.

In one embodiment, due to SIB1size constraints, caused by coverage requirements, SIB1may not be able to include the additional information. The added information may be then included in other SIBs or possibly, e.g., through a new extension of SIB1. In the latter case, the current SIB1may include an indicator that “Cell Access Related Information” is extended, so that the UE also reads this (updated) information before judging if the cell is “suitable” for camping.

The UE52may perform PLMN selection (or the UE may have already performed this PLMN selection earlier in the manner discussed hereinbefore). In any event, by way of example, it is seen from block86inFIG. 10that UE's currently registered (or selected) PLMN is PLMN-2. When the UE52enters the coverage of the Shared HeNB56, it receives the SIB1message85and checks SIB1's contents. As UE's currently registered PLMN is PLMN-2, the UE52may be mainly interested in information related to this PLMN. First, as indicated at block87, the UE52may check the CSG Indication for PLMN-2and may find out that the HeNB's cell is a Closed CSG cell for this PLMN-2(as the CSG Indication for this PLMN is “TRUE” in the SIB1message85). It is understood that when a CSG Indication field is set to “TRUE,” the UE may be only allowed to access the CSG cell if the corresponding PLMN's CSG-ID matches an entry in the UE-based Allowed CSG List. Thus, in the example inFIG. 10, the UE may then check, as indicated at block88inFIG. 10, the CSG-ID (in the received SIB1message85) for PLMN-2and may find out that this value is CSG-ID22. As the UE52holds the combination {PLMN-2, CSG-ID22} in its Allowed CSG List (block84,FIG. 10), it knows that it is allowed to access this cell associated with the Shared HeNB56. The UE52may then. “camp on” this CSG cell.

As mentioned above in conjunction with discussion ofFIG. 7, in one embodiment, in addition to the steps illustrated inFIG. 10, the UE52may also indicate to the network (through the HeNB56) in further signaling which CSG-ID it is accessing when performing the network access. Thus, in the embodiment ofFIG. 10, the UE52may send the CSG-ID22(of PLMN-2) to the network when the UE finds a matching entry for this CSG-ID in its Allowed CSG List. If CSG sub-identifiers (as discussed with reference toFIG. 7) are also provided in the SIB1message from the Shared HeNB, the UE may also report one or more of these sub-identifiers to the HeNB (as discussed hereinbefore) when there are matching entries for these sub-identifiers in UE's Allowed CSG List.

FIG. 11is a block diagram of an exemplary mobile handset or UE52according to one embodiment of the present invention. The UE52may include a transceiver90, an antenna91, a processor92, and a memory94(which may, in some embodiments, also include memory on UE's SIM card). In particular embodiments, some or all of the functionalities described above (e.g., reception of SI from the HeNB56via the antenna91and transceiver90; storage of EPLMN list and Allowed CSG List in the memory94; transmission of PLMN selection information and CSG-ID and CSG sub-identifiers for the selected PLMN to HeNB56via transceiver90and antenna91; etc.) as being provided by mobile communication devices or other forms of UE may be provided by the UE processor92executing instructions stored on a computer-readable medium, such as the memory94shown inFIG. 11. Alternative embodiments of the UE52may include additional components beyond those shown inFIG. 11that may be responsible for providing certain aspects of the UE's functionality, including any of the functionality described above and/or any functionality necessary to support the solution described above.

FIG. 12is a block diagram of an exemplary HeNB or a similar mobile communication node (or base station)56according to one embodiment of the present invention. The HeNB56may include a baseband processor95to provide radio interface with the mobile handsets (in the carrier network54) via HeNB's Radio Frequency (RF) transmitter96and RF receiver98units coupled to the HeNB antenna59. The processor95may be configured (in hardware and/or software) to provide enhanced SI to the UE52as per the teachings of the present invention. In one embodiment, the processor95may also receive various intimations from the UE52(e.g., intimation of selection of PLMN and its CSG-ID, etc.) via the receiver98, whereas HeNB's transmissions to the UE52may be carried out via the transmitter96. The baseband processor95may include a processing unit99in communication with a memory102to process and store relevant information for the cell. A scheduler (e.g., the scheduler104inFIG. 12) in the HeNB56may provide the scheduling decision for UE52based on a number of factors such as, for example, QoS (Quality of Service) parameters, UE buffer status, uplink channel quality report received from UE52, UE capabilities, etc. The scheduler104may have the same data structure as a typical scheduler in an eNB in an LTE system.

The processor95may also provide additional baseband signal processing (e.g., mobile device registration, channel signal information transmission, radio resource management, etc.) as required. The processing unit99may include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. Some or all of the functionalities described above as being provided by a mobile base station, a base station controller, a node B, an enhanced node B, an HeNB, an HNB, a home base station, a femtocell base station, and/or any other type of mobile communications node may be provided by the processing unit99executing instructions stored on a computer-readable data storage medium, such as the memory102shown inFIG. 12.

The HeNB56may further include a timing and control unit105and a core network interface unit106as illustrated inFIG. 12. The control unit105may monitor operations of the processor95and the network interface unit106, and may provide appropriate timing and control signals to these units. The interface unit106may provide a bi-directional interface for the HeNB56to communicate with the core network58to facilitate administrative and call-management functions for mobile subscribers operating in the carrier network54through HeNB56.

Alternative embodiments of the base station56may include additional components responsible for providing additional functionality, including any of the functionality identified above and/or any functionality necessary to support the solution described above. Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. The methodology provided herein (related to CSG handling through enhanced SI) may be implemented in a computer program, software, or firmware incorporated in a computer-readable storage medium (e.g., the memory102inFIG. 12and memory94inFIG. 11) for execution by a general purpose computer or a processor (e.g., the processor92inFIG. 11and processing unit99inFIG. 12). Examples of computer-readable storage media include a Read Only Memory (ROM), a Random Access Memory (RAM), a digital register, a cache memory, semiconductor memory devices, magnetic media such as internal hard disks, magnetic tapes and removable disks, magneto-optical media, and optical media such as CD-ROM disks and Digital Versatile Disks (DVDs).

The foregoing describes a system and method for enhanced support for handling of Closed Subscriber Groups (CSGs) and RAN-sharing for home base stations and other small cells. The present invention enables indication of multiple CSG IDs and CSG Indications in the System Information (SI) sent on the cell broadcast channel, thereby making it possible to support different CSG IDs and CSG Indications for every PLMN Identity (PLMN-ID) and also to support a PLMN-ID with multiple associated CSG IDs and CSG Indications. This makes it possible to have different CSG IDs for different operators and even to have multiple CSG IDs for one operator (i.e., a single PLMN). The present invention also makes it possible to selectively use the CSG concept for some PLMNs (as given by their respective CSG Indications), but not for all. The present invention thus improves the possibility to cost-effectively provide enhanced support for RAN-sharing for HeNBs or other base stations using a network's existing radio resources and signaling framework (i.e., without significant disruption to network architecture or functionality). This enhanced support may be useful in opening up new business cases where third party operators deploy a network of base stations (e.g., a RAN) that can be shared by multiple operators, leading to better cellular coverage, peak rates, and capacity.

It is noted here that although the foregoing discussion focuses on sharing of HeNBs through enhanced SI in E-UTRAN, the teachings of the present invention are exemplary in nature and are not confined to implementation in E-UTRAN only. Rather, the teachings of the present invention related to enhanced support for CSG-handling and RAN-sharing through enhanced SI may be applied, with suitable modifications (as may be apparent to one skilled in the art using the present teachings), to other wireless systems or networks as well, such as, for example, networks/systems using 3G/4G specifications. Some examples of such systems or networks include, but not limited to, Global System for Mobile communications (GSM) networks, LTE networks, LTE-Advanced networks, UTRAN networks, Wideband Code Division Multiple Access (WCDMA) systems, WCDMA-based HSPA systems, CDMA2000 systems, GSM/Enhanced Data Rate for GSM Evolution (GSM/EDGE) systems, and WiMAX systems.