Base-station-to-base-station gateway and related devices, methods, and systems

The present disclosure relates to a base-station-to-base-station (BS-BS) gateway in a Long Term Evolution (LTE) cellular communication network and methods of operation thereof. In one embodiment, the BS-BS gateway receives information from a first base station which includes a hostname and a network address of the first base station. The BS-BS gateway then stores a mapping between the hostname and the network address. Thereafter, in one embodiment, the BS-BS gateway enables a second base station to address messages to the first base station using the hostname of the first base station. In this manner, changes in the network address of the first base station will not affect the ability of the second base station to address messages to the first base station. In some embodiments, the first base station is a low-power base station (LP-BS) and the second base station is a high-power base station (HP-BS).

FIELD OF THE DISCLOSURE

The present disclosure relates to a base-station-to-base-station gateway in a cellular communication network.

BACKGROUND

A conventional Long Term Evolution (LTE) cellular communication network10, as shown inFIG. 1, includes a Radio Access Network (RAN)12including a number of Evolved/E-UTRAN Node Bs (eNBs)14-1through14-3(generally referred to herein collectively as eNBs14and individually as eNB14) that provide wireless radio access to wireless devices, otherwise known as user equipment devices (UEs) (not shown). The eNBs14communicate with one another via X2 connections and communicate with a core network16via S1 connections. The core network16includes one or more Mobility Management Entities (MMEs)18, which are control nodes that are responsible for, among other things, tracking UEs as they move through the LTE cellular communication network10. The MMEs18are also responsible for assigning the UEs to Serving-Gateways (S-GWs)20. The S-GWs20route and forward user data packets, while also acting as mobility anchors for the user plane during inter-eNB handovers and as anchors for mobility between LTE and other 3rdGeneration Partnership Project (3GPP) technologies.

FIG. 2illustrates a heterogeneous deployment of both eNBs14and Home Evolved/E-UTRAN Node Bs (HeNBs)22-1through22-3(generally referred to herein collectively as HeNBs22and individually as HeNB22) that has been proposed to improve coverage and increase capacity of the LTE cellular communication network10. The addition of low-power base stations (LP-BSs), such as the HeNBs22, to the LTE cellular communication network10poses new problems not present in a conventional homogeneous cellular communication network. Like the eNBs14, the HeNBs22use S1 connections to communicate with the core network16(not shown) and X2 connections to communicate with other HeNBs22and eNBs14. In particular, there is a need for systems and methods that improve management of X2 communication between base stations and, in particular, between the eNB14and the HeNBs22.

SUMMARY

The present disclosure relates to a base-station-to-base-station (BS-BS) gateway in a cellular communication network and methods of operation thereof. In one embodiment, the BS-BS gateway receives information from a first base station which includes a hostname and a network address of the first base station. The BS-BS gateway then stores a mapping between the hostname and the network address. Thereafter, in one embodiment, the BS-BS gateway enables a second base station to address messages to the first base station using the hostname of the first base station. In this manner, changes in the network address of the first base station will not affect the ability of the second base station to address messages to the first base station. In some embodiments, the first base station is a low-power base station (LP-BS) and the second base station is a high-power base station (HP-BS). As used herein “low-power base station” and “high-power base station” may be used to distinguish between base stations based on their permanent capabilities, current configuration, and/or their operation at a specific instant. Thus, in particular embodiments that include both low-power base stations and high-power base stations, a low-power base station may represent a device with comparable or identical components and capabilities to those of the high-power base stations but that is merely configured differently from, or operating in a different manner from, the high-power base stations at a given point in time.

In a further embodiment, the cellular communication network is a Long Term Evolution (LTE) cellular communication network and the BS-BS gateway is an X2 Gateway (X2-GW). Further, in one embodiment, the X2-GW receives the information including the hostname and network address via a Stream Control Transmission Protocol (SCTP) INIT message from the LP-BS (e.g., a Home Evolved/E-UTRAN Node B (HeNB)). In one embodiment, the hostname of the LP-BS is a Fully Qualified Domain Name (FQDN) determined from a Global eNB Identity of the LP-BS.

In one embodiment, a BS-BS gateway receives a connection initiation from a first base station to initiate a connection to a second base station. The BS-BS gateway then informs the first base station that the BS-BS gateway is a BS-BS gateway. Further, in one embodiment, the cellular communication network is an LTE cellular communication network and the BS-BS gateway is an X2-GW. Still further, in one embodiment, the first base station is an HP-BS, and the second base station is an LP-BS.

In one embodiment, a BS-BS gateway receives a message from a first base station where the destination is identified as a hostname of a second base station. The BS-BS gateway then obtains the network address of the second base station from a mapping between a hostname of the second base station and a network address of the second base station, and sends the message to the second base station using the network address of the second base station. Further, in one embodiment, the BS-BS gateway is an X2-GW. Still further, in one embodiment, the first base station is an HP-BS, and the second base station is an LP-BS.

In one embodiment, a base station determines its own hostname and network address. The base station then sends information including the hostname and network address to a BS-BS gateway. In one embodiment, the cellular communication network is an LTE cellular communication network, the BS-BS gateway is an X2-GW, and the base station sends the information including the hostname and network address of the base station to the X2-GW via an SCTP INIT message.

DETAILED DESCRIPTION

The present disclosure relates to managing base-station-to-base-station (BS-BS) communication connections in a cellular communication network. While the embodiments described below are for a Long Term Evolution (LTE) cellular communication network, the present disclosure is not limited thereto. The concepts disclosed herein are applicable to any suitable type of cellular communication network. As such, while LTE terminology is sometimes used herein, such terminology should not be construed as limiting the scope of this disclosure. Additionally, as used herein, the term LTE encompasses both LTE and LTE Advanced.

Before describing various embodiments of the present disclosure, a discussion of some particular issues related to X2 connection management in the heterogeneous deployment of a conventional LTE cellular communication network10illustrated inFIG. 2is beneficial. As illustrated inFIG. 2, the heterogeneous deployment of the conventional LTE cellular communication network10includes Evolved/E-UTRAN Node Bs (eNBs)14as well as Home Evolved/E-UTRAN Node Bs (HeNBs)22, which are used to extend the coverage area and increase the capacity of the conventional LTE cellular communication network10. The addition of the HeNBs22to the conventional LTE cellular communication network10poses new problems not present in a conventional homogeneous cellular communication network.

One such problem results from additional X2 connections required for the HeNBs22. As a result of the additional X2 connections, there is a significant increase in resources at the eNB14needed to manage the X2 connections. More specifically, for effective administration of a Radio Access Network (RAN)12, it is desirable for each eNB14to have X2 connections with all of its neighbors, which in this case include both neighboring eNBs14and neighboring HeNBs22. The increase in the number of X2 connections increases the amount of resources necessary for creating and maintaining these communication connections.

Another problem is that while most eNBs14are designed to be reliable and have high uptime, the HeNBs22may be powered down frequently. Power-down of the HeNBs22breaks the corresponding X2 connections to the neighboring eNBs14and the neighboring HeNBs22. This can lead to additional resources being spent as the neighboring eNBs14and the neighboring HeNBs22attempt to reestablish the X2 connections, which can in turn impair the efficiency of the RAN12. Furthermore, especially for the HeNBs22, which may use a backhaul network that is not otherwise part of the LTE cellular communication network10(e.g., a home broadband connection), the network addresses, which are sometimes referred to as Transport Network Layer (TNL) addresses, may be different upon coming back online after power-down. This makes it more difficult for the neighboring eNBs14and the neighboring HeNBs22to reestablish the X2 connections after the HeNB22comes back online, which again impairs the efficiency of the RAN12.

Systems and methods that address the aforementioned issues in the conventional LTE cellular communication network10are disclosed herein. In this regard,FIG. 3illustrates a heterogeneous LTE cellular communication network24according to one embodiment of the present disclosure. The heterogeneous LTE cellular communication network24includes a RAN26, which includes eNBs28-1through28-3(generally referred to herein collectively as eNBs28and individually as eNB28) that provide wireless radio access for one or more wireless devices, which for LTE are referred to as user equipment devices (UEs) (not shown). The RAN26also includes HeNBs30-1through30-3(generally referred to herein collectively as HeNBs30and individually as HeNB30) that also provide wireless radio access to one or more UEs. It is important to remember that the HeNBs30are used only as an example of the concepts disclosed herein, but the concepts disclosed herein are equally applicable to any type(s) of low-power base stations (LP-BSs) (e.g., LP-BSs for femtocells, picocells, microcells, or the like). These LP-BSs generally serve a smaller area than high-power base stations (HP-BSs) such as the eNBs28. For example, some LP-BSs, such as HeNBs30, are deployed in individual residences or small businesses.

The eNBs28and the HeNBs30communicate with each other via X2 connections. Note that while many of the embodiments disclosed herein focus on BS-BS communication (e.g., X2 communication) between HP-BSs and LP-BSs, the concepts disclosed herein are also applicable to BS-BS communication between base stations of the same type (e.g., between two HP-BSs or between two LP-BSs). BS-BS communication over X2 connections is used to, for example, coordinate connection handovers and perform load management between the eNBs28and the HeNBs30. In LTE, these BS-BS communications (which for LTE are also referred to herein as X2 communications) are sent over an Internet Protocol (IP) network using Stream Control Transmission Protocol (SCTP) as the transport layer for control messages.

The eNBs28communicate with a core network32of the heterogeneous LTE cellular communication network24via corresponding S1 connections. Likewise, while not illustrated, the HeNBs30also communicate with the core network32via corresponding S1 connections. In LTE, S1 control messages are also sent over an IP network using SCTP as the transport layer. The core network32includes one or more Mobility Management Entities (MMEs)34and one or more Serving Gateways (S-GWs)36. The MMEs34are control nodes for the heterogeneous LTE cellular communication network24that are responsible for, among other things, tracking UEs as the UEs move through the heterogeneous LTE cellular communication network24. The MMEs34are also responsible for assigning the UEs to the S-GWs36. The S-GWs36operate to, among other things, route and forward user data packets, while also acting as mobility anchors for the user plane during inter-base-state handovers and as anchors for mobility between LTE and other 3rdGeneration Partnership Project (3GPP) technologies.

The heterogeneous LTE cellular communication network24also includes an X2 Gateway (X2-GW)40for X2 connections between the eNBs28and the HeNBs30. In this particular example, the X2 connections between the eNB28-2and the HeNBs30are provided via the X2-GW40. Likewise, the X2 connections between the eNB28-3and the HeNBs30are provided via the X2-GW40. For security reasons, traffic over the X2 connections will preferably be encrypted using IP Security (IPsec) tunnels which authenticate and encrypt every IP packet. If the X2-GW40is considered to be located at a trusted site, it may have one IPsec tunnel between the eNB28-2and X2-GW40, for instance, and one IPsec tunnel between the X2-GW40and each HeNB30-1through30-3. This means that the X2-GW40can interact with the IP packets in order to decrypt and re-encrypt the packets as needed, according to one embodiment. The X2-GW40is beneficial for the eNBs28-2and28-3because each of the eNBs28-2and28-3maintains only one SCTP transport layer connection to the X2-GW40instead of separate SCTP transport layer connections for each X2 connection for each of the HeNBs30.

As discussed below in detail, in one embodiment, the X2-GW40creates mappings between hostnames and network addresses for the HeNBs30. However, it should be noted that the X2-GW40may additionally or alternatively be used to create mappings between hostnames and network addresses for the eNBs28. Using the mappings, the X2-GW40is enabled to route X2 messages addressed with the hostnames of the HeNBs30from the eNBs28-2and28-3to the appropriate HeNBs30. Among other things, this may allow for faster X2 connection reestablishment between eNBs28and HeNBs30when the network address of any of the eNBs28or HeNBs30changes for any reason, including if an eNB28or an HeNB30is assigned a different network address upon coming back online after power-down. This is only a benefit of one preferred embodiment and does not limit the present disclosure thereto.

In addition to routing messages addressed with hostnames, the X2-GW40enables the eNBs28and/or the HeNBs30to query the X2-GW40for the network address of a desired HeNB30based on the hostname of the desired HeNB30. Specifically, an eNB28or HeNB30can query the X2-GW40with a hostname. The X2-GW30then looks up the corresponding network address and returns the network address to the eNB28or the HeNB30that issued the query.

Notably, the X2-GW40is not limited to the functions described above. For instance, as discussed below in detail, in one embodiment, the X2-GW40can also notify the eNBs28and/or HeNBs30that an eNB28or HeNB30to which they are connected through X2 connections is unavailable. This reduces the resources being spent attempting to reestablish the X2 connections with the eNB28or HeNB30that is unavailable.

Before further discussing embodiments of the present disclosure, a brief review of the SCTP protocol used for the X2 connections is beneficial. SCTP is defined in Request for Comments (RFC) 4960. SCTP is designed for signaling transport over IP networks. SCTP is connection-oriented and provides signaling means between endpoints. An SCTP packet is made of two parts: (1) a common header containing source and destination information and (2) one or more chunks. A chunk includes either control information or user data. While not essential for understanding the concepts disclosed and claimed herein, for more information regarding SCTP, the interested reader is directed to RFC 4960, “Stream Control Transmission Protocol,” published in September 2007.

FIG. 4illustrates the field format for an SCTP chunk42within an SCTP packet. The SCTP chunk42comprises a Chunk Type field44, a Chunk Flags field46, a Chunk Length field48, and a Chunk Value field50. The Chunk Type field44includes a chunk type of the SCTP chunk42, where the chunk type identifies the type of information contained in the Chunk Value field50and takes a value of between 0 and 254. The value of 255 is reserved for future use as an extension field. RFC 4960 defines the chunk types illustrated in Table 1 below.

An SCTP packet including a chunk of INIT chunk type is used to establish a connection between two endpoints. The INIT chunk contains some mandatory fields as well as some variable fields. The variable fields are given below in Table 2.

TABLE 2Variable ParameterStatusType ValueIPv4 AddressOptional5IPv6 AddressOptional6Cookie PreservativeOptional9Reserved for ECNOptional32768 (0x8000)CapableHost Name AddressOptional11Supported AddressOptional12Types
In more detail, the IPv4 Address field is 32 bits (unsigned integer) and contains an IPv4 address of the sending endpoint. It is binary encoded. An IPv4 Address parameter indicates a network address the sending endpoint of the INIT chunk will support for the connection being initiated. The IPv6 Address field is 128 bits (unsigned integer) and contains an IPv6 (RFC2460) address of the sending endpoint. It is binary encoded. An IPv6 Address parameter indicates a network address the sending endpoint of the INIT chunk will support for the connection being initiated. The Host Name Address field can be used by the sending endpoint of INIT chunk to pass its hostname (in place of its IP addresses) to the recipient endpoint. The recipient endpoint is responsible for resolving the hostname.

The INIT ACK chunk type is used to acknowledge the initiation of an SCTP connection (i.e., an SCTP association). The ABORT chunk type is used to immediately close, or terminate, the connection. The ABORT chunk may contain Cause Parameters to inform the recipient endpoint about the reason for the abort. A description of the causes is given below with respect to the ERROR chunk type. The SHUTDOWN chunk type is sent to initiate a graceful close of the connection with the recipient endpoint. In contrast to the ABORT chunk type, the SHUTDOWN chunk type allows any buffers to be emptied and other control messages to be processed while the connection is terminated.

The ERROR chunk type is used to notify the sending endpoint's peer (i.e., the recipient endpoint) of certain error conditions. An ERROR chunk contains one or more causes. An ERROR chunk is not considered fatal to the connection in and of itself, but may be used with an ABORT chunk to report a fatal condition. The Cause Code of an ERROR chunk defines the type of error condition being reported. Defined Cause Codes are given in Table 3 below.

FIG. 5illustrates one instance of the SCTP chunk42, where the SCTP chunk42is more specifically an ERROR chunk52. As illustrated, the Chunk Value field50includes a Cause Code field54, a Cause Length field56, and an Upper Layer Abort Reason field58. In this particular example, the Cause Code field54is set to “12,” which is a User Initiated Abort. The User Initiated Abort Cause Code indicates that the ERROR chunk52was sent because of an upper-layer request. The upper layer can specify an Upper Layer Abort Reason that is transported transparently by SCTP in the Upper Layer Abort Reason field58. The Upper Layer Abort Reason may be delivered to the upper layer at the recipient endpoint.

FIG. 6illustrates the operation of the heterogeneous LTE cellular communication network24ofFIG. 3where the X2-GW40obtains mappings of hostnames to network addresses of the HeNBs30according to one embodiment of the present disclosure. The HeNBs30-1through30-3first determine their own hostnames and network addresses (steps100-1through100-3). The network address of the HeNB30is, in one embodiment, an IP address of the HeNB30, which can be obtained or otherwise determined by the HeNB30using any suitable technique. In one embodiment, the hostname of the HeNB30is a Fully Qualified Domain Name (FQDN) of the HeNB30, which, in one embodiment, can be determined by the HeNB30using an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Cell Global Identifier (ECGI) of the HeNB30. More specifically,FIGS. 7A and 7Billustrate components of an ECGI. The ECGI is a concatenation of a Public Land Mobile Network (PLMN) ID and an E-UTRAN Cell Identifier (ECI). Furthermore, the PLMN is a concatenation of a Mobile Country Code (MCC) that identifies the country where the mobile network is located and a Mobile Network Code (MNC) that identifies the network operator. Additionally, the ECI, as shown inFIG. 7A, is a concatenation of an eNB ID (20 bits) which uniquely identifies a base station in a mobile network and a Cell ID (8 bits) which identifies a specific cell served by the base station. In the case of an HeNB30and some other LP-BSs, the base station has only one cell, such that all the digits of the ECI (28 bits) are devoted to unique base station identification, as shown inFIG. 7B.

Returning toFIG. 6, according to one embodiment, the HeNB30determines the FQDN of the HeNB30based on the following string:henbID<ENBID>.mnc<MNC>.mcc<MCC>.3gppnetwork.org
where <ENBID>, <MNC>, and <MCC> are replaced with the values of the ENBID, MNC, and MCC of the HeNB30. The FQDN is then used as the hostname of the HeNB30. In other embodiments, combinations of values such as Tracking Area Code (TAC), Tracking Area Identity (TAI), and Closed Subscriber Group (CSG) ID are used to create a hostname. Note that this is just one embodiment. The FQDN may be determined using any suitable formula or means. Further, the hostname is not limited to an FQDN of the HeNB30. Any type of suitable hostname may be used.

The HeNBs30-1through30-3then send SCTP INIT messages, including both the hostnames and the network addresses of the HeNBs30-1through30-3, to the X2-GW40(steps102-1through102-3). In one embodiment, in order to determine the network address of the X2-GW40, the HeNBs30determine the FQDN of the X2-GW40based on the following string: x2gw.tac-lb<TAC-low-byte>.tac-hb<TAC-high-byte>.mnc<MNC>.mcc<MCC>.3gppnetwork.org. The HeNBs30then query a Domain Name System (DNS) server using the FQDN to obtain the network address of the X2-GW40. More specifically, using the HeNB30-1as an example, the HeNB30-1sends an SCTP message including an INIT chunk (this SCTP message is referred to herein as an SCTP INIT message) to the X2-GW40, where the INIT chunk includes the hostname of the HeNB30-1in the corresponding parameter field of the INIT chunk. The network address of the HeNB30-1can also be included in the corresponding parameter field of the INIT chunk or, alternatively, may be determined by, for example, the sender address in the IP packet header. In this manner, the HeNBs30sends information to the X2-GW40including the hostnames and the network addresses of the HeNBs30via SCTP INIT messages according to one embodiment of the present disclosure. Note that the SCTP INIT messages are just one preferred embodiment. The HeNBs30may send the information including the hostnames and network addresses to the X2-GW40using any suitable message or message type.

Upon receiving the SCTP INIT messages from the HeNBs30-1through30-3, the X2-GW40stores corresponding mappings between the hostnames and the network addresses of the HeNBs30(steps104-1through104-3). In this way, the X2-GW40creates mappings between hostnames and network addresses for the HeNBs30. According to one embodiment of the present disclosure, new mappings are established as new HeNBs30are brought online or initiate X2 connections with the X2-GW40. Further, in one embodiment, the mappings may also be updated as the HeNBs30change their network addresses and/or hostnames.

FIG. 8illustrates the operation of the X2-GW40ofFIG. 3where the X2-GW40enables addressing of X2 messages between the eNBs28and the HeNBs30using the hostnames of the HeNBs30, according to one embodiment of the present disclosure. An eNB28first obtains a network address for an HeNB30and a network address for the X2-GW40associated with the HeNB30(step200). According to one embodiment of the present disclosure, step200is the Automatic Neighbor Relation (ANR) and TNL address discovery process ofFIG. 9(described below), but the present disclosure is not limited thereto. Next, the eNB28initiates an X2 connection by sending an SCTP INIT message to the X2-GW40(step202). Notably, at the time of initiating the X2 connection, in this embodiment, the eNB28does not know that the X2-GW40is in fact an X2-GW. Rather, the eNB28may only be aware that the network address obtained for the X2-GW40is a network address of a gateway such as a Security Gateway (SeGW). In some embodiments, the functionality of the X2-GW40and the SeGW can be combined into a single gateway. In other embodiments, the X2-GW40and the SeGW can be implemented separately. This transparency enables the procedures of the eNB28to be unaffected by the presence of the X2-GW40. If the eNB28does not know how to take advantage of the features of the X2-GW40, the legacy procedures will still be operational. This is only a benefit of one preferred embodiment, and does not limit the present disclosure thereto.

The X2-GW40then sends an SCTP message back to the eNB28informing the eNB28that the X2-GW40is an X2-GW40(step204). In one embodiment, this SCTP message is an SCTP ERROR message (i.e., an SCTP message including an ERROR chunk) that includes the User Initiated Abort Cause Code along with an Upper Layer Abort Reason that indicates that the X2-GW40is an X2-GW. By informing the eNB28that the X2-GW40is an X2-GW, the eNB28is enabled to take advantage of the functionality of the X2-GW40(e.g., send X2 messages through the X2-GW40addressed via appropriate hostnames).

In this embodiment, the eNB28then sends a message addressed to the HeNB30using the hostname of the HeNB30(step206). The X2-GW40obtains the network address of the HeNB30from the mapping between the hostname and the network address of the HeNB30(step208). In this manner, the X2-GW40translates, or resolves, the hostname of the HeNB30to the network address of the HeNB30. The X2-GW40then forwards the message to the HeNB30using the network address of the HeNB30(step210). Enabling the eNB28to address messages to the HeNB30using the hostname of the HeNB30in this manner provides many advantages. While not being limited to or by any particular advantage, as one example, changes in the network address of the HeNB30will not affect the ability of the eNB28to address messages to the HeNB30. This is useful, for example, because HeNBs30are more likely to use a backhaul network that is not otherwise part of the LTE cellular communication network10(e.g., a home broadband connection) and the network address of the HeNB30may change. Enabling the eNB28to address messages to the HeNB30using the hostname of the HeNB30reduces the time and resources required to reestablish a connection between the eNB28and the HeNB30, since the eNB28will not be required to query via the MME34or some other core network32element to determine the new network address of the HeNB30.

FIG. 9illustrates a process by which an eNB28ofFIG. 3receives configuration information about an HeNB30via an ANR and TNL address discovery process, where the configuration information enables the eNB28to establish an X2 connection to the HeNB30via the X2-GW40according to one embodiment of the present disclosure. A UE60first detects a Physical Cell ID (PCI) of the HeNB30(step300). The UE60then determines if signal measurements for the HeNB30meet one or more predefined reporting criteria (step302). The reporting criteria can include signal strength according to one embodiment of the present disclosure. If the reporting criteria have been met, the UE60sends a measurement report to the eNB28with which the UE60is already associated (step304).

The eNB28analyzes the measurement report to determine if the measurement report is associated with a source that is unknown to the eNB28and is a candidate to become a neighbor. This process is one of many adopted by 3GPP and implemented in the standards of LTE that work toward a planned Self Organizing Network (SON). If the eNB28determines that additional information about the HeNB30is needed (step306), the eNB28requests additional information about the HeNB30from the UE60(step308). The additional information requested by the eNB28may include one or more desired or relevant parts of system information broadcast by the HeNB30. As an example, the eNB28may request the ECGI of the HeNB30. The UE then obtains the additional information from the HeNB30(step310) and reports the additional information to the eNB28(step312).

The eNB28then uses this information, such as the ECGI of the HeNB30, to query via an MME34, or other element of the core network32, requesting configuration information for the HeNB30(step314). The MME34then queries the HeNB30requesting configuration information for the HeNB30(step316). The HeNB30then sends the configuration information for the HeNB30to the MME34that includes the network address for the HeNB30and the network address for the X2-GW40associated with the HeNB30(step318). The MME34sends the configuration information for the HeNB30to the eNB28that includes the network address for the HeNB30and the network address for the X2-GW40associated with the HeNB30(step320). In one embodiment, the X2-GW40is not identified as such in the configuration information. Also, in one embodiment, the network addresses are IP addresses; however, the present disclosure is not limited thereto.

While the eNBs28are designed to be reliable and have high uptime, there may still be times when the eNBs28are not available. This could be due to unforeseen circumstances or scheduled maintenance, for example. Due to the possible modularity and more personal aspect of HeNBs, in some embodiments, the HeNBs30may be powered down more frequently than the eNBs28, or may otherwise become unavailable. This unavailability of an eNB28or an HeNB30can have a negative impact on the efficiency of the RAN26, among other things. According to one embodiment, when the eNB28or the HeNB30determines that the eNB28or the HeNB30is transitioning to an unavailable state, the eNB28or the HeNB30notifies one or more radio network nodes of the unavailability of the eNB28or the HeNB30. As used herein, radio network nodes may refer to base stations (such as eNBs28and HeNBs30), BS-BS gateways (such as an X2-GW40), or any other node in the radio access network. This notification will, among other things, reduce the attempts to reestablish an X2 connection between the eNBs28or the HeNBs30(or the X2-GW40) and the now unavailable eNB28or HeNB30. This is only a benefit of one preferred embodiment, and does not limit the present disclosure thereto.

In this regard,FIGS. 10A and 10Billustrate the operation of the heterogeneous LTE cellular communication network24ofFIG. 3where an HeNB30indirectly notifies one or more eNBs28that the HeNB30is unavailable via the X2-GW40, according to one embodiment of the present disclosure.FIG. 10Aillustrates a scenario where the eNB28ceases communication attempts with the HeNB30until the eNB28is notified that the HeNB30is available. Conversely,FIG. 10Billustrates a scenario where the eNB28ceases communication attempts with the HeNB30for a specific period of time. In another embodiment, the eNB28ceases communication attempts with the HeNB30until the eNB28receives information from a UE indicating that the HeNB30is available. This might occur, for instance, as part of an ANR process as described with regard toFIG. 9.

InFIG. 10A, first the HeNB30determines that it is transitioning to an unavailable state (step400). This determination can be in response to the HeNB30being powered down or otherwise transitioning to unavailability. Next, the HeNB30notifies the X2-GW40that the HeNB30is unavailable (step402). In one embodiment, this notification is accomplished by sending an SCTP message over an X2 connection. More specifically, the message could be an SCTP message with a SHUTDOWN chunk or an ERROR chunk with a predefined reason in the Upper Layer Abort Reason field58that indicates that the HeNB30is unavailable. This message could, for example, encode that the HeNB30is powering down, or even that the HeNB30is an HeNB and that it is powering down. Note that the SCTP message is just one preferred embodiment and that the notification can be accomplished using any suitable means. This notification is similar to the deactivation message that the eNBs28are enabled to send when disabling cells for energy savings. Currently, it is possible to include a Deactivation Indication IE with a value “deactivated” in an “eNB Configuration Update” message sent from an eNB28or an HeNB30to another eNB28or HeNB30. One possibility is to extend this with a dedicated value for “power down,” “HeNB power down,” or some similar dedicated value.

Upon being notified that the HeNB30is unavailable, the X2-GW40then notifies one or more eNBs28-1through28-3with which the HeNB30has an X2 connection that the HeNB30is unavailable (steps404-1through404-3). In order to accomplish this, in one embodiment, the X2-GW40uses a table indicating, for each associated eNB28and HeNB30, a list of other eNBs28and HeNBs30to which the eNB28/HeNB30has X2 connections to each other eNB28and HeNB30. This table can be produced by any suitable means. As one example, the X2-GW40could compile such a table during the process described in step202ofFIG. 8where an eNB28initiates a connection to an HeNB30using the X2-GW40as a gateway.

The eNBs28-1through28-3then cease communication attempts with the HeNB30until the eNBs28-1through28-3are notified that the HeNB28is again available (steps406-1through406-3). In this embodiment, sometime thereafter, the HeNB30determines that the HeNB30is in an available state (step408) and, in response, notifies the X2-GW40that the HeNB30is available (step410). The X2-GW40then notifies the one or more eNBs28-1through28-3that the HeNB30is available (steps412-1through412-3). After the one or more eNBs28-1through28-3are notified that the HeNB30is available, the one or more eNBs28-1through28-3reestablish the X2 communication connections with the HeNB30(steps414-1through414-3). While they are not shown, there can be several other messages between the eNBs28, the HeNB30, and the X2-GW40in order to reestablish X2 communication.

InFIG. 10B, first the HeNB30determines that it is transitioning to an unavailable state (step500). This determination can be in response to the HeNB30being powered down or otherwise transitioning to unavailability. Next, the HeNB30notifies the X2-GW40that the HeNB30is unavailable (step502). In one embodiment, this notification is accomplished by sending an SCTP message over an X2 connection. More specifically, the message could be an SCTP message with a SHUTDOWN chunk or an ERROR chunk with a predefined reason in the Upper Layer Abort Reason field58that indicates that the HeNB30is unavailable. Note that the SCTP message is just one preferred embodiment and that the notification can be accomplished using any suitable means. The X2-GW40then notifies one or more eNBs28-1through28-3with which the HeNB30has an X2 connection that the HeNB30is unavailable (steps504-1through504-3). The eNBs28-1through28-3then cease communication attempts with the HeNB30for a predetermined time period (steps506-1through506-3). In one embodiment, after the predetermined time period has expired, the one or more eNBs28-1through28-3attempt to reestablish the X2 communication connections with the HeNB30(steps508-1through508-3).

In some embodiments, it is not necessary for an HeNB30to notify other elements in the heterogeneous LTE cellular communication network24about the unavailability of the HeNB30. In this regard,FIG. 11illustrates the operation of the heterogeneous LTE cellular communication network24ofFIG. 3according to one embodiment of the present disclosure where the X2-GW40directly notifies one or more eNBs28that an HeNB30is unavailable as determined by the X2-GW40. First, the X2-GW40determines that an HeNB30is unresponsive (step600). This determination can be in response to, for example, repeated failed attempts to contact the HeNB30by the X2-GW40. The X2-GW40then notifies one or more eNBs28-1through28-3with which the HeNB30has an X2 connection that the HeNB30is unavailable (steps602-1through602-3). In order to accomplish this, in one embodiment, the X2-GW40uses a table indicating, for each associated eNB28and HeNB30, a list of other eNBs28and HeNBs30to which the eNB28/HeNB30has X2 connections to each other eNB28and HeNB30. This table can be produced by any suitable means. As one example, the X2-GW40could compile such a table during the process described in step202ofFIG. 8where an eNB28initiates a connection to an HeNB30using the X2-GW40as a gateway. The one or more eNBs28-1through28-3then cease communication attempts with the HeNB30(steps604-1through604-3).

In this embodiment, the X2-GW40subsequently determines that the HeNB30is again in an available state (step606). The X2-GW40then notifies the one or more eNBs28-1through28-3that the HeNB30is available (steps608-1through608-3). After the one or more eNBs28-1through28-3are notified that the HeNB30is available, the one or more eNBs28-1through28-3reestablish the X2 communication connections with the HeNB30(steps610-1through610-3). As discussed above, while they are not shown, there can be several other messages between the eNBs28, the HeNB30, and the X2-GW40in order to reestablish X2 communication.

FIGS. 10A, 10B, and 11illustrate embodiments in which an eNB28is notified of the unavailability of an HeNB30via the X2-GW40. However, the present disclosure is not limited thereto. More generally, the concepts disclosed herein can be used by any base station to directly notify another base station of its unavailability. In this regard,FIG. 12illustrates one embodiment of the heterogeneous LTE cellular communication network24in which the HeNBs30directly notify other HeNBs30and/or eNB(s)28with which they have X2 connections when the HeNBs30become unavailable. The same process can be used by the eNB(s)28to notify other eNBs28and/or HeNB(s)30with which they have X2 connections when the eNB(s)28become unavailable.

FIGS. 13A and 13Billustrate the operation of the heterogeneous LTE cellular communication network24ofFIG. 12where an HeNB30directly notifies one or more eNBs28that the HeNB30is unavailable according to one embodiment of the present disclosure.FIG. 13Aillustrates the scenario where the eNB28ceases communication attempts with the HeNB30until the eNB28is notified that the HeNB30is available. Conversely,FIG. 13Billustrates the scenario where the eNB28ceases communication attempts with the HeNB30for a specific period of time.

InFIG. 13A, first the HeNB30determines that it is transitioning to an unavailable state (step700). This determination can be in response to the HeNB30being powered down or otherwise transitioning to unavailability. Next, in response to determining that the HeNB30is transitioning to the unavailable state, the HeNB30notifies the eNB28that the HeNB30is unavailable (step702). In one embodiment, this notification is accomplished by sending an SCTP message over an X2 connection. More specifically, the message could be an SCTP message with a SHUTDOWN chunk or an ERROR chunk with a predefined reason in the Upper Layer Abort Reason field58that indicates that the HeNB30is unavailable. Note that the SCTP message is just one preferred embodiment and that the notification can be accomplished using any suitable means. The eNB28then ceases communication attempts with the HeNB30until the eNB28is notified that the HeNB30is available again (step704). In this embodiment, sometime thereafter, the HeNB30determines that the HeNB30is in an available state (step706) and, in response, notifies the eNB28that the HeNB30is available (step708). Lastly, after the eNB28is notified that the HeNB30is available, the eNB28reestablishes the X2 communication connection with the HeNB30(step710).

InFIG. 13B, first the HeNB30determines that it is transitioning to an unavailable state (step800). This determination can be in response to the HeNB being powered down or otherwise transitioning to unavailability. Next, the HeNB30notifies the eNB28that the HeNB30is unavailable (step802). In one embodiment, this notification is accomplished by sending an SCTP message over an X2 connection. As described above with regard toFIG. 13A, the message could be an SCTP message with a SHUTDOWN chunk or an ERROR chunk with a predefined reason in the Upper Layer Abort Reason field58that indicates that the HeNB30is unavailable. Note that the SCTP message is just one preferred embodiment and that the notification can be accomplished using any suitable means. The eNB28then ceases communication attempts with the HeNB30for a predetermined time period (step804). In one embodiment, after the predetermined time period has expired, the eNB28attempts to reestablishes the X2 communication connection with the HeNB30(step806).

FIG. 14is a block diagram of one of the eNBs28ofFIG. 3according to one embodiment of the present disclosure. As illustrated, the eNB28includes a communication subsystem62, a radio subsystem64that includes one or more radio units (not shown), and a processing subsystem66that includes storage68. The communication subsystem62generally includes analog and, in some embodiments, digital components for sending and receiving communications to and from the X2-GW40and in some embodiments, the HeNBs30and/or other eNBs28. The radio subsystem64generally includes analog and, in some embodiments, digital components for wirelessly sending and receiving messages to and from the UE60in the heterogeneous LTE cellular communication network24.

The processing subsystem66is implemented in hardware or in a combination of hardware and software. In particular embodiments, the processing subsystem66may comprise, for example, one or several general-purpose or special-purpose microprocessors or other microcontrollers programmed with suitable software and/or firmware to carry out some or all of the functionality of the eNB28described herein. In addition or alternatively, the processing subsystem66may comprise various digital hardware blocks (e.g., one or more Application Specific Integrated Circuits (ASICs), one or more off-the-shelf digital and analog hardware components, or a combination thereof) configured to carry out some or all of the functionality of the eNB28described herein. Additionally, in particular embodiments, the above-described functionality of the eNB28may be implemented, in whole or in part, by the processing subsystem66executing software or other instructions stored on a non-transitory computer-readable medium, such as Random Access Memory (RAM), Read Only Memory (ROM), a magnetic storage device, an optical storage device, or any other suitable type of data storage component.

FIG. 15is a block diagram of one of the HeNBs30ofFIG. 3according to one embodiment of the present disclosure. As illustrated, the HeNB30includes a communication subsystem70, a radio subsystem72that includes one or more radio units (not shown), and a processing subsystem74that includes storage76. The communication subsystem70generally includes analog and, in some embodiments, digital components for sending and receiving communications to and from the X2-GW40, and in some embodiments, the eNBs28and other HeNBs30. The radio subsystem72generally includes analog and, in some embodiments, digital components for wirelessly sending and receiving messages to and from the UE60in the heterogeneous LTE cellular communication network24.

The processing subsystem74is implemented in hardware or in a combination of hardware and software. In particular embodiments, the processing subsystem74may comprise, for example, one or several general-purpose or special-purpose microprocessors or other microcontrollers programmed with suitable software and/or firmware to carry out some or all of the functionality of the HeNB30described herein. In addition or alternatively, the processing subsystem74may comprise various digital hardware blocks (e.g., one or more ASICs, one or more off-the-shelf digital and analog hardware components, or a combination thereof) configured to carry out some or all of the functionality of the HeNB30described herein. Additionally, in particular embodiments, the above-described functionality of the HeNB30may be implemented, in whole or in part, by the processing subsystem74executing software or other instructions stored on a non-transitory computer-readable medium, such as RAM, ROM, a magnetic storage device, an optical storage device, or any other suitable type of data storage component.

FIG. 16is a block diagram of the X2-GW40ofFIG. 3according to one embodiment of the present disclosure. As illustrated, the X2-GW40includes a communication subsystem78and a processing subsystem80that includes storage82. The communication subsystem78generally includes analog and, in some embodiments, digital components for sending and receiving communications to and from the HeNBs30and eNBs28. The storage82can be on a non-transitory computer-readable medium, such as RAM, ROM, a magnetic storage device, an optical storage device, or any other suitable type of data storage component.

The processing subsystem80is implemented in hardware or in a combination of hardware and software. In particular embodiments, the processing subsystem80may comprise, for example, one or several general-purpose or special-purpose microprocessors or other microcontrollers programmed with suitable software and/or firmware to carry out some or all of the functionality of the X2-GW40described herein. In addition or alternatively, the processing subsystem80may comprise various digital hardware blocks (e.g., one or more ASICs, one or more off-the-shelf digital and analog hardware components, or a combination thereof) configured to carry out some or all of the functionality of the X2-GW40described herein. Additionally, in particular embodiments, the above-described functionality of the X2-GW40may be implemented, in whole or in part, by the processing subsystem80executing software or other instructions stored on a non-transitory computer-readable medium, such as RAM, ROM, a magnetic storage device, an optical storage device, or any other suitable type of data storage component.

The following acronyms are used throughout this disclosure.3GPP 3rdGeneration Partnership ProjectANR Automatic Neighbor RelationASIC Application Specific Integrated CircuitBS Base StationBS-BS GW Base Station to Base Station GatewayCSG Closed Subscriber GroupDNS Domain Name SystemE-UTRAN Evolved Universal Terrestrial Radio Access NetworkECGI E-UTRAN Cell Global IdentifierECI E-UTRAN Cell IdentifiereNB Evolved/E-UTRAN Node BFQDN Fully Qualified Domain NameHeNB Home Evolved/E-UTRAN Node BHP-BS High-Power Base StationIMSI International Mobile Subscriber IdentityIP Internet ProtocolIPsec IP SecurityLP-BS Low-Power Base StationLTE Long Term EvolutionMCC Mobile Country CodeMME Mobility Management EntityMNC Mobile Network CodePCI Physical Cell IDPLMN Public Land Mobile NetworkRAM Random Access MemoryRAN Radio Access NetworkROM Read Only MemorySCTP Stream Control Transmission ProtocolS-GW Serving GatewaySeGW Security GatewaySON Self Organizing NetworkTAC Tracking Area CodeTAI Tracking Area IdentityTNL Transport Network LayerUE User Equipment DeviceX2-GW X2 Gateway