Abstract:
Femtocell radio access network (RAN) devices are typically small, low-cost base stations that may be deployed in areas, for example, where macro-cellular RAN coverage is poor or congested. Thus, wireless communication devices (WCDs) using femtocell devices may benefit from improved wireless coverage, while traffic is offloaded from the macro-cellular RAN. As the use of femtocell devices in residences and businesses continues to grow, it may be advantageous to allow WCD users to use telephony devices coupled to the femtocell device to answer incoming calls for their WCDs. For example, a femtocell device may receive an incoming call request for a WCD, determine that the WCD is eligible for an extended handset service, and then cause a telephony device to alert for the incoming call request.

Description:
BACKGROUND 
     Femtocell devices typically provide wireless telephony and/or data services to a limited geographical region, such as a residence or a business. A femtocell device may be deployed in such a region to provide base transceiver station (BTS) functions, base station controller (BSC) functions, or both, to wireless communication devices (WCDs). Consequently, a femtocell device may radiate to define one or more wireless coverage areas. Such an arrangement can provide wireless coverage to locations that may not be well-served by macro-cellular wireless coverage areas. Femtocell devices may also be low-cost (at least when compared to analogous macro-cellular devices), and may exhibit a relatively small physical size. 
     OVERVIEW 
     The embodiments herein are directed to a femtocell device that allows the user of a WCD to receive calls for the WCD at one or more telephony devices while the WCD is within one of the wireless coverage areas defined by the femtocell device. Thus, for example, the user may utilize the femtocell device in his or her residence to provide supplemental wireless coverage for the user while he or she is at the residence. Preferably, the WCD is subscribed to a wireless service provider and the femtocell device connects to the wireless service provider via a packet-switched interface. The femtocell device may also contain a telephony interface that couples to telephony wiring within the residence. The user may have connected, for example, one or more plain old telephony service (POTS) devices (e.g., standard telephones) to this wiring. 
     When the user enters the vicinity of the residence, the WCD may register with the femtocell device for an extended handset service. Once the WCD is registered for this service, the WCD may make outgoing calls via the wireless coverage area(s) defined by the femtocell device. However, incoming calls for the WCD that arrive at the femtocell device may be routed via the telephony interface to one or more telephony devices, thereby causing these devices to ring. As a result, the user does not have to carry the WCD with himself or herself while in the residence. Instead, the user can answer incoming calls at any available telephony device. 
     This feature can be selectively enabled or disabled on a per WCD basis. Thus, the user may activate this feature only for WCDs of individuals who live at the residence. In this way, visitors who bring their WCDs to the residence can take advantage of the femtocell&#39;s wireless coverage without answering their incoming calls via the residence&#39;s telephony device(s). Further, based on the WCD being called, the femtocell device may cause the telephony device(s) to play out a distinctive ring that identifies the called WCD. 
     Therefore, in an example embodiment, a femtocell device may be communicatively coupled to a packet-switched network and to at least one telephony device. Preferably, the femtocell device radiates to define a wireless coverage area that is operable to serve WCDs. The femtocell device may receive a registration request for wireless service from a WCD. This registration request may contain a WCD identifier (e.g., a phone number) that identifies the WCD. 
     In response to receiving the registration request, the femtocell device may determine that (i) the WCD is served by the wireless coverage area, and (ii) the WCD identifier is in a whitelist of WCDs permitted to use the extended handset service. In response to making these determinations, the femtocell device may (i) register the WCD so that the WCD is eligible for the extended handset service, and (ii) transmit a registration confirmation to the WCD. 
     When receiving an incoming call request from a correspondent node seeking to establish a call to the WCD, the femtocell device may cause the telephony device to alert. Particularly, in response to receiving the incoming call request, the femtocell device may check the whitelist and determine that the WCD is eligible for the extended handset service. Then, the femtocell device may cause the telephony device to, for example, ring. If the telephony device is answered, the femtocell device may bridge the call between the correspondent node and the telephony device, so that the call can be carried out without direct involvement of the WCD. 
     These and other aspects and advantages will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, it should be understood that this overview and other description throughout this document is merely for purposes of example and is not intended to limit the scope of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a network architecture, in accordance with an example embodiment; 
         FIG. 2  is a block diagram of a femtocell device, in accordance with an example embodiment; 
         FIG. 3  is another block diagram of a femtocell device, including the femtocell device&#39;s connectivity to other devices and networks, in accordance with an example embodiment; 
         FIG. 4  is a message flow, in accordance with an example embodiment; 
         FIG. 5  is another message flow, in accordance with an example embodiment; 
         FIG. 6  is a flow chart, in accordance with an example embodiment; and 
         FIG. 7  is another flow chart, in accordance with an example embodiment. 
     
    
    
     DESCRIPTION 
     In accordance with example embodiments, methods and devices for providing an extended handset service for femtocell devices are presented. Preferably, a femtocell device is arranged to provide wireless service to nearby WCDs and is communicatively coupled to a packet-switched network and at least one telephony device. When a WCD attempts to register with the femtocell device for wireless service, the femtocell device may determine that the WCD is eligible for the extended handset service. The extended handset service may be a feature of the femtocell device that routes incoming call requests for WCDs to the telephony device(s). Thus, in response to receiving an incoming call request that seeks to establish a call with the WCD, the femtocell device may determine that the WCD is eligible for the extended handset service, and responsively cause the telephony device, rather than the WCD, to alert for the incoming call request. Alternatively, the femtocell device may cause both the telephony device and the WCD to alert. 
     I. System Architecture 
       FIG. 1  shows a block diagram of a communication network  100  that may be operated by a wireless service provider, and in which example embodiments can be deployed. Communication network  100  may operate according to various technologies including, but not limited to, Code-Division Multiple Access (CDMA), Worldwide Interoperability for Microwave Access (WIMAX®), Universal Mobile Telecommunications System (UMTS®), Long Term Evolution (LTE®), IDEN®, or 802.11 (Wifi). Thus, users may engage in communication via WCDs that support one or more of these or other technologies. 
     As shown, a WCD  102  may communicate with a macro-cellular radio access network (RAN)  101  over an air interface  103 - a . In particular, air interface  103 - a  may be provided by BTS  104 , which may be coupled or integrated with a BSC  106 . WCD  102  is also shown as having an air interface  103 - b  with a femtocell device  126 . 
     Transmissions over air interface  103 - a  from BTS  104  to WCD  102  may utilize a “forward link,” while transmissions over interface  103 - a  from WCD  102  to BTS  104  may utilize a “reverse link.” Similarly, transmissions over air interface  103 - b  from femtocell device  126  to WCD  102  may utilize a forward link, while transmissions over air interface  103 - b  from WCD  102  to femtocell device  126  may utilize a reverse link. Each forward link and reverse link may comprise one or more logical traffic channels. Furthermore, the links of air interfaces  103 - a  and  103 - b  could be active concurrently or at different times, depending on the operational state of WCD  102 , the physical location of WCD  102  with respect to BTS  104  and femtocell device  126 , and the type of communication session WCD  102  seeks or is engaged in. 
     BSC  106  may serve to control assignment of traffic channels (e.g., over air interface  103 - a ). BSC  106  may also be connected to a mobile switching center (MSC)  108 , which in turn may provide access to wireless circuit-switched services such as circuit-voice and circuit-data. It should be understood that the term radio network controller (RNC) can also be used to refer to a BSC, or a combination BTS/BSC. 
     As represented by its connection to public-switched telephone network (PSTN)  110 , MSC  108  may also be coupled with one or more other MSCs, other telephony circuit switches in the wireless service operator&#39;s (or in a different operator&#39;s) network, or other wireless communication systems. In this way, wireless communication network  100  may support user mobility across MSC regions, roaming between wireless service operators, and local and long-distance landline telephony services. Alternatively, part or all of MSC  108  may be replaced by softswitch components (not shown) that transport voice and other media over packet-switched networks. 
     BSC  106  may also be connected to an access network authentication, authorization, and accounting (AN-AAA) server  112 . AN-AAA server  112  may support link-level authentication and authorization for WCD data sessions. Data transport may be provided by way of a communicative link between BSC  106  and a packet-data serving node (PDSN)  114 , which in turn may provide connectivity with the wireless service provider&#39;s core packet-data network  116 . Nodes that may reside within or adjunct to core packet-data network  116  are, by way of example, an authentication, authorization, and accounting (AAA) server  118 , a mobile-IP home agent (HA)  120 , and a border router (BR)  122 . 
     PDSN  114  may be a router-like device that manages the connectivity of WCDs to a packet-switched network, such as the core packet-data network  116 , the Internet  124 , or one or more private IP networks (not shown). In an example embodiment, PDSN  114  may serve tens, hundreds or thousands of WCDs via point to point protocol (PPP) links to each of these WCDs. However, a PPP link to a WCD is not required for PDSN  114  to serve a WCD. Preferably, PDSN  114  is also capable of serving as a mobile-IP foreign agent. 
     HA  120  is preferably an anchor point for WCDs that support mobile-IP. While a WCD, such as WCD  102 , may change its point of attachment from one foreign agent to another (e.g., from one PDSN to another) as it roams between wireless coverage areas, WCD  102  preferably maintains a registration with the same HA. Furthermore, in order to maintain a substantially static home IP address, the WCD may receive a home IP address assignment from an HA. 
     AAA server  118  may provide network- and service-layer authentication and authorization support, and could be combined with AN-AAA server  112 . Accordingly, AAA server  118  may support one or more of the well known AAA protocols such as RADIUS and/or DIAMETER. AAA server  118  may maintain a profile for each WCD registered with the wireless service provider. Further, AAA server  118  may maintain profiles for other WCDs as well. Such a profile may contain an indication of the identity of each WCD and the WCD&#39;s subscriber (e.g., the WCD&#39;s user). For example, a profile for a given WCD may include the given WCD&#39;s network access identifier (NAI), mobile directory number (MDN), international mobile subscriber identifier (IMSI), electronic serial number (ESN), and/or mobile equipment identifier (MEID). Such a profile may also include a username, a password, and/or any other information associated with the given WCD. Preferably, PDSN  114 , HA  120 , or both authenticate WCD sessions and/or service requests from WCDs with AAA server  118 . 
     BR  122  may seek to provide secure connectivity to the Internet  124 . To that end, BR  122  could include a firewall, packet filter, and/or other security mechanisms. Thus, BR  122  may serve to protect core packet-data network  116 , as well as macro-cellular RAN  101  in general, from potential attacks (e.g., hacking attempts, denial of service attacks, viruses, or malware) emanating from the Internet  124  or other IP networks. 
     Core packet-data network  116  could comprise one or more additional switches, routers, and gateways (not shown) that collectively provide transport and interconnection among the various entities and networks of macro-cellular RAN  101 . In this context, for instance, core packet-data network  116  could be an overlay on, or a sub-network of, one or more additional networks. 
     Macro-cellular RAN  101  may also include a virtual private network (VPN) terminator  128 . VPN terminator  128  may be a standalone component or combined with BR  122 , HA  120 , or other components of macro-cellular RAN  101 . VPN terminator  128  may serve as an endpoint for secure connections with authorized devices seeking access to macro-cellular RAN  101  via unsecure, external networks such as the Internet  124 . For instance, femtocell device  126  may connect to Internet  124  over a broadband connection  127  (e.g., a cable modem, digital subscriber line (DSL), or T-carrier connection) and then to VPN terminator  128 . Femtocell device  126  could include a VPN client component that establishes a secure tunnel with VPN terminator  128 , such that packet-data communications over the secure tunnel between femtocell device  126  and VPN terminator  128  can then take place securely. Secure tunnels can be implemented according such protocols as IP Security (IPsec), although other mechanisms may be employed. 
     Assuming a secure VPN connection is established between femtocell device  126  and VPN terminator  128 , femtocell device  126  may then communicate securely with other entities in macro-cellular RAN  101  by way of the VPN terminator  128 . In particular, femtocell device  126  may receive configuration and messaging data and other operational parameters from a femtocell controller  130 . Femtocell controller  130  may also provide similar control and services for other femtocell devices connected to network macro-cellular RAN  101 . 
     A femtocell switch  132  may act as a signaling gateway between MSC  108  and VPN terminator  128 , enabling WCDs communicating via a femtocell device, such as WCD  102  via femtocell device  126 , to engage in calls via MSC  108  to other wireless devices, as well as over PSTN  110 . Media translation between packet-based media and circuit-based media may be carried out by a media gateway (MG)  134 . Thus, femtocell device  126  may transmit packetized data to MG  134  via VPN terminator  128 . MG  134  may, in turn, translate or transcode the data to circuit-based media for transmission on PSTN  110 , for example. MG  134  may perform the reverse translation for transmission in the opposite direction. 
     It should be understood that a femtocell device may be considered to be form of micro-type RAN. Preferably, a femtocell device is deployed on user premises, such as within a residence or within a business, to provide additional wireless network coverage to that residence or business. However, femtocell devices can, in general, be deployed anywhere to provide wireless network coverage. Thus, wireless coverage areas defined by femtocell devices may overlap with wireless coverage areas from one or more macro-cellular RANs. WCDs may seek to register with either a femtocell device or a macro-cellular RAN based on the respective signal strengths that the WCD receives from each of these devices, and/or based on other factors. For instance a WCD may be arranged to prefer using a femtocell device over a macro-cellular RAN when both are available. 
     Furthermore, a femtocell device typically has a small form factor, as least when compared to that of a macro-cellular RNC, so that the femtocell device can be easily deployed in a particular location, or moved between locations. Thus, for instance, femtocell devices may be sold directly to consumers, in stores or online, and may be deployed by consumers in a residential or business network. As discussed above, a femtocell device may be directly or indirectly coupled to a residential or business broadband network service, such as a cable modem, DSL, or T-carrier connection, so that the femtocell device can communicate via the Internet. This use of wireline access to the Internet serves to offload traffic from macro-cellular RANs. 
     With respect to the various business entities involved in communication network  100 , it is generally assumed throughout this specification that femtocell device  126  is provided by, or at least associated with, the same wireless service provider that operates macro-cellular RAN  101 . But, this need not be the case. Various business models may be in place through which other entities provide, manage, and/or support femtocell device  126 . Additionally, it is also generally assumed that the individual who uses WCD  102  is an account holder for both WCD  102  and femtocell device  126  (i.e., the individual is a subscriber of the wireless service provider and his or her service plan includes WCD  102  and femtocell device  126 ). But again, this need not be the case. 
     It should also be understood that the depiction of just one of each network component in  FIG. 1  is illustrative, and there could be more than one of any component. Communication network  100  may also contain other types of components not shown. Alternatively or additionally, any network component in  FIG. 1  could be omitted, or combined with another network component, without departing from the scope of the invention. Thus, the particular arrangement shown in  FIG. 1  should not be viewed as limiting with respect to the present invention. 
     Further, the network components that make up a wireless communication system such as communication network  100  may be implemented as a combination of one or more integrated and/or distributed platforms, each comprising one or more computer processors, one or more forms of computer-readable storage (e.g., disks drives, random access memory, etc.), one or more communication interfaces for interconnection between components and the network and operable to transmit and receive the communications and messages described herein, and one or more computer software programs and related data (e.g., machine-language instructions and program and user data) stored in the one or more forms of computer-readable storage and executable by the one or more computer processors to carry out the functions, steps, and procedures of the various embodiments of the present invention described herein. 
     To that end,  FIG. 2  is a simplified block diagram exemplifying femtocell device  126  and illustrating some of the functional components that would likely be found in a femtocell device arranged to operate in accordance with the embodiments herein. Such a femtocell device could include, for example, the functionality of any type of RAN component, such as a BTS, a BSC, an RNC, a PDSN, a BR, and so on. 
     Femtocell device  126  preferably includes a processor  202 , a data storage  204 , a network interface  206 , and an input/output function  208 , all of which may be coupled by a system bus  210  or a similar mechanism. Processor  202  preferably includes one or more CPUs, such as one or more general purpose processors and/or one or more dedicated processors (e.g., application specific integrated circuits (ASICs) or digital signal processors (DSPs), etc.) Data storage  204 , in turn, may comprise volatile and/or non-volatile data storage and can be integrated in whole or in part with processor  202 . 
     Data storage  204  preferably holds program instructions executable by processor  202 , and data that is manipulated by these instructions, to carry out the various methods, processes, or functions described herein. Alternatively, these methods, processes, or functions can be defined by hardware, firmware, and/or any combination of hardware, firmware and software. By way of example, the data in data storage  204  may contain program instructions executable by processor  202  to carry out any of the methods, processes, or functions disclosed in this specification or the accompanying drawings. 
     Network interface  206  may take the form of one or more wireless and/or wireline interfaces. For example, network interface  206  may comprise transceiver(s) that radiate to define a wireless coverage area. This wireless coverage area may include an air interface, such as air interface  103 - b , for engaging in communication with WCDs. Network interface  206  may also comprise a wireline interface, for example to a broadband connection, to communicate with the Internet or other IP networks. Network interface may additionally comprise a telephony interface to communicate with telephony devices. Accordingly, network interface  206  may take the form of one or more wireless or wireline interfaces. However, other forms of physical layer connections and other types of standard or proprietary communication protocols may be used with network interface  206 . 
     Input/output function  208  facilitates user interaction with example femtocell device  126 . Input/output function  208  may comprise multiple types of input devices, such as a keyboard, a mouse, a touch screen, and so on. Similarly, input/output function  208  may comprise multiple types of output devices, such as a monitor, printer, or one or more light emitting diodes (LEDs). Additionally or alternatively, femtocell device  126  may support remote access from another device, via network interface  206  or via another interface (not shown), such an RS-232 or universal serial bus (USB) port. 
       FIG. 3  provides another view of femtocell device  126  and its potential connectivity. Via a broadband interface  310 , femtocell device  126  may be communicatively coupled to Internet  124 . Via Internet  124 , femtocell device  126  may receive calls routed from both RAN  101  and PSTN  110 . Preferably, these calls would be initiated via a packet-switched signaling call control protocol, such as the Session Initiation protocol (SIP) or H.323. Broadband interface  310  may be, for example, an Ethernet jack. Instead of or in addition to being communicatively coupled to Internet  124 , femtocell device may be communicatively coupled to one or more private IP networks, or directly to RAN  101 . 
     Via a wireless interface  316 , femtocell device  126  may radiate to define one or more wireless coverage areas, which may provide wireless services to WCD  302  and WCD  304 . These wireless services may include voice and data services, and may be based on CDMA, WIMAX®, UMTS®, LTE®, IDEN®, and/or Wifi technologies. Thus, wireless interface  316  may be, for example, a wireless transceiver. 
     Via a telephony interface  318 , femtocell device  126  may provide telephony services to telephony device  306  and telephony device  308 . Preferably, telephony interface  318  is a standard telephony jack, such as an RJ11 jack, that can be connected via telephone wire to the in-building telephone wiring (e.g., a twisted pair of copper wiring) of residential or business premises. However, other types of interfaces may be used. For instance, telephony interface  318  could be an Integrated Services Digital Network (ISDN), centrex, or enterprise voice over IP interface. Telephony interface  318  could also be a cordless phone interface or another type of wireless interface (e.g., BLUETOOTH® or Wifi). 
     Through such an interface, femtocell device  126  may provide basic wireline telephony functions to telephony device  306  and telephony device  308 , such as power, battery backup, dialed-digit collection, dial tone, ringing indications (for both incoming calls and outgoing calls), and full-duplex voice transport. In addition to these basic services, femtocell device  126  may also support any additional services that might be found in a class 5 telephony switch, a centrex switch, a subscriber line interface circuit (SLIC) device, or any type of device that provides a foreign exchange service (FXS) to telephony devices. Thus, telephony interface  318  may be able to detect when one of telephony device  306  and telephony device  308  goes “off hook,” and then provide dial tone to this device. Similarly, when an incoming call arrives at femtocell device  126 , telephony interface  318  may generate voltage to cause telephony device  306  and/or telephony device  308  to ring. 
     In addition to the three interfaces shown in  FIG. 3 , femtocell device  126  may comprise a telephony multimedia terminal adapter (MTA)  312  and a wireless MTA  314 . These MTAs may be hardware and/or software components of femtocell device  126 . Preferably, telephony MTA  312  serves to translate between the signaling and bearer data formats of Internet  124  and telephony interface  318 . Thus, for example, telephony MTA  312  may receive call signaling messages (e.g., incoming call requests in SIP or H.323 format) via broadband interface  310 , and use these messages to trigger activity on telephony device  306  and/or telephony device  308  (e.g., to cause these devices to ring). These call signaling messages may originate from a correspondent node on Internet  124 , PSTN  110 , or RAN  101 . Additionally, in response to receiving an off-hook indication and dual-tone multi-frequency (DTMF) digits from one of telephony device  306  and telephony device  308 , telephony MTA  312  may generate a call signaling message for transmission, via broadband interface  310 , to a correspondent node. When a call is established between telephony device  306  and a correspondent node, and/or between telephony device  308  and a correspondent node, telephony MTA  312  may translate between the bearer data formats supported by broadband interface  310  (e.g., the Real Time Protocol (RTP)) and telephony interface  318  (e.g., baseband voice). 
     Preferably, wireless MTA  314  serves to translate between the signaling and bearer data formats of RAN  101  and those supported by telephony MTA  312 , as well as the signaling and bearer data formats of RAN  101  and those supported by wireless interface  316 . Thus, for example, wireless MTA  314  may receive, via broadband interface  310 , call signaling messages from RAN  101 . In one possible embodiment, these call signaling messages may conform to Third Generation Partnership Project 2 (3GPP2) Specification X.S0059-200-0 Version 1.0, entitled “cdma2000 Femtocell Network: 1x and IMS Network Aspects,” which is incorporated by reference in its entirety herein. Specification X.S0059-200-0 defines how to encapsulate, into a SIP message, at least some of the information typically found in communications between an MSC and a BSC. The communication protocols defined in Specification X.S0059-200-0 may be referred to as the A1p interface, and packets containing information arranged according to Specification X.S0059-200-0 may be referred to as being in the A1p format. 
     Thus, for example, wireless MTA  314  may receive, via broadband interface  310  and from RAN  101 , a SIP INVITE message in the A1p format. This message may contain a page request for WCD  302 . In response to receiving this message, wireless MTA  314  may cause wireless interface  316  to transmit one or more paging messages over an air interface to WCD  302 . WCD  302  may respond to being paged by transmitting a page response message, also over the air interface, to femtocell device  126 . This page response message may be received by broadband interface  310  and routed to wireless MTA  314 . Wireless MTA  314  may then translate this page response message into the A1p format and transmit the resulting A1p message, via broadband interface  310 , to RAN  101 . Wireless MTA  314  may also translate between the bearer data formats supported by RAN  101  and wireless interface  316 . 
     In another example, wireless MTA  314  may translate call signaling messages between A1p format and SIP format used by telephony MTA  312 . Thus, if wireless MTA  314  receives, via broadband interface  310 , call signaling messages in A1p format, wireless MTA  314  may translate the messages to SIP format, and transmit the messages to telephony MTA  312 . Conversely, if wireless MTA  314  receives, from telephony MTA  312 , call signaling messages in SIP format, wireless MTA  314  may translate these messages to A1p format, and transmit the messages via broadband interface  310  to RAN  101 . 
     The functions of telephony MTA  312  and wireless MTA  314  may be combined into a common MTA, or further sub-divided into additional logical components. Further, it should be understood that A1p and SIP protocols are not required for the functioning of telephony MTA  312  and/or wireless MTA  314 , and other protocols may be used instead. 
     II. Example Femtocell Device Procedures 
       FIGS. 4 ,  5 ,  6 , and  7  are example message flows and flow charts that illustrate functions of femtocell device  126 , including operations that may be carried out by telephony MTA  312  and/or wireless MTA  314 . However, these message flows and flow charts are not intended to be comprehensive, and have been simplified for purposes of presentation. Thus, each of these message flows and flow charts may include more or fewer steps than provided in  FIGS. 4 ,  5 ,  6 , and  7 , and any one of these message flows and flow charts may be combined with any other without departing from the scope of the invention. 
     Further, portions of any of these example message flows and flow charts that are depicted in  FIGS. 4 ,  5 ,  6 , and  7  as being performed at femtocell device  126  could alternatively be performed at other network devices. For instance, translation between various incoming call request formats could take place at femtocell switch  132  instead of at femtocell device  126 . 
     At a high level,  FIGS. 4 ,  5 ,  6 , and  7  address various ways in which femtocell device  126  can redirect an incoming call for a WCD served by femtocell  126  to a telephony device communicatively coupled to femtocell device  126 . In addition to or instead of this extended handset service functionality, femtocell device  126  may be able to provide other features as well. 
       FIG. 4  provides an example registration message flow  400 . Via message flow  400 , WCD  302  may register for wireless service with femtocell device  126 . As a result of this registration, femtocell device  126  may additionally register WCD  302  for the extended handset service. At step  402 , WCD  302  may transmit a registration request to femtocell device  126 . This transmission may be triggered by WCD  302  coming within range of a wireless coverage area defined by femtocell device  126 . The registration request may take the form of WCD  302  registering for wireless service with femtocell device  126 . 
     At step  404 , femtocell device  126  may transmit the registration request in A1p format to RAN  101 . Preferably, the registration request that femtocell device  126  transmits at step  404  is based on the registration request that femtocell device  126  received from WCD  302 . For example, the registration request that femtocell device  126  transmits at step  404  may be a location update request containing the one or more WCD identifiers (e.g., an IMSI, MDN, NAI, MEID, and/or ESN) assigned to WCD  302 . 
     At step  406 , in response to receiving this registration request, RAN  101  may associate WCD  302  with femtocell device  126 . In this way, when RAN  101  receives, for example, an incoming call, text message, or multimedia message for WCD  302 , RAN  101  may forward the incoming call, text message, or multimedia message to femtocell device  126  for eventual delivery to WCD  302 . RAN  101  may also carry out additional steps not shown in message flow  400 , such as authenticating WCD  302 . 
     At step  408 , RAN  101  may transmit a registration confirm to femtocell device  126 . Preferably, this registration confirm is in A1p format and serves to notify femtocell device  126  that WCD  302  is registered for wireless service. In response to receiving the registration confirm, femtocell device  126  may determine whether WCD  302  is eligible for the extended handset service. Alternatively, RAN  101  may determine whether WCD  302  is eligible for the extended handset service and transmit the result of this determination to femtocell device  126 . 
     To that point, at step  410 , femtocell device  126  may check a WCD whitelist. Preferably, the WCD whitelist contains zero or more WCD identifiers assigned to WCDs that are eligible for the extended handset service. Thus, if a WCD identifier of WCD  302  is in the whitelist, WCD  302  is eligible for the extended handset service. However, if a WCD identifier of WCD  302  is not in the whitelist, WCD  302  is not eligible for the extended handset service. The whitelist may be stored at femtocell device  126  or at some other networked device such that the whitelist is accessible to femtocell device  126 . In one possible embodiment, a party that controls femtocell device  126  configures the whitelist to include WCD identifiers of WCDs that are permitted to use the extended handset service. 
     In message flow  400 , it is assumed that a WCD identifier of WCD  302  is in the whitelist. Therefore, at step  412 , femtocell device  126  may register WCD  302  for the extended handset service. For example, the femtocell device may place an identifier of WCD  302  in an extended handset service registration database. Preferably, all WCDs registered for the extended handset service are listed in this database, while WCDs not registered for the extended handset service are not listed in the database. Listed WCDs may be indexed in the database by one or more of their respective WCD identifiers. At step  414 , femtocell device  126  may transmit the registration confirm message to WCD  302 . 
     Once registered for the extended handset service, a user of WCD  302  may take advantage of this service as shown in  FIG. 5 .  FIG. 5  provides an example message flow  500  for an incoming call that is redirected from WCD  302  to telephony device  306 , in accordance with the extended handset service. 
     At step  502 , femtocell device  126  receives, via RAN  101  and from a correspondent node, an incoming call request for WCD  302 . Preferably, the incoming call request is in the A1p format. Femtocell device  126  may then route the incoming call request to wireless MTA  314 . At step  504 , in response to receiving the incoming call request, wireless MTA  314  may look up WCD  302  in the extended handset service registration database. 
     Finding WCD  302  in the database, at step  506 , wireless MTA  314  may translate the incoming call request from the A1p format to SIP format. Then, at step  508 , wireless MTA  314  may transmit the incoming call request (now in SIP format) to telephony MTA  312 . In response to receiving the incoming call request, telephony MTA  312  may translate the incoming call request to telephony format (e.g., POTS format). Then, at step  512 , telephony MTA  312  transmits the incoming call request (now in telephony format) to telephony device  306 . Thus, in an embodiment wherein telephony interface  318  is a POTS interface and telephony device  306  is a POTS device, telephony MTA  312  may carry out step  512  by generating voltage that causes telephony device  306  to produce a ringing indication at step  514 . If telephony device  306  is answered, femtocell device  126  may bridge the call between the correspondent node and telephony device  306 . 
     It should be understood that steps  506 ,  508  and  510  may be combined into a single step. For instance, femtocell device  126  may combine the functions of telephony MTA  312  and wireless MTA  314 , and may translate the incoming call request directly from A1p format to telephony format. It should also be understood that the ringing indication of step  514  may be any type of alerting mechanism. Thus, for example, telephony device  306  may play out an audible ringtone, vibrate, and/or produce a visible indication of an incoming call on a display. If multiple telephony devices are coupled to the telephony interface  318 , telephony MTA  312  may cause more than one of these telephony devices to alert. 
     The alerting mechanism may be based on the WCD being called. Thus, for example, the femtocell device may cause the telephony device(s) to play out a distinctive ring that identifies the called WCD. One way in which the femtocell device may do so is for the femtocell device to generate voltage in different patterns for different WCDs. For instance, the femtocell device may generate voltage for a duration of one second to indicate that a first WCD is being called, but generate voltage for two half-second durations, with a quarter-second pause in between, to indicate that a second WCD is being called. In full generality, these distinctive rings can take any form, such as distinctive musical ringtones or distinctive patterns of vibrations. 
     If the incoming call request is for a WCD that is not registered for the extended handset service (e.g., WCD  304 ), then wireless MTA  314  may transmit the incoming call request (translated to a different format if necessary) to WCD  304  via wireless interface  316 . In this way, a user of femtocell device  126  may configure femtocell device  126  to only provide the extended handset service to a limited number of WCDs. For instance, if a user of WCD  302  lives or works at the location of femtocell device  126 , the party controlling femtocell device  126  may configure femtocell device  126  to allow the user of WCD  302  to take advantage of the extended handset service. Thus, while WCD  302  is registered with femtocell device  126 , the user of WCD  302  can answer incoming calls for WCD  302  at any telephony device coupled to femtocell device  126 . On the other hand, if a user of WCD  304  is just a visitor to the location of femtocell device  126 , the party controlling femtocell device  126  may configure femtocell device  126  to provide wireless service to WCD  304 , so that incoming calls for WCD  304  are not redirected to telephony devices coupled to femtocell device  126 . 
       FIG. 6  is a flow chart  600  of steps that may occur at a femtocell device to support the procedures of, or similar to, that of message flow  400 . Accordingly, at step  602 , a femtocell device may receive an incoming call request for a WCD. At step  604 , in response to receiving the incoming call request, the femtocell device may determine that the WCD is eligible for an extended handset service. Then, in response to determining that the WCD is eligible for the extended handset service, the femtocell device may cause a telephony device to alert for the incoming call request. 
     Likewise,  FIG. 7  is a flow chart  700  of steps that may occur at a femtocell device to support the procedures of, or similar to, that of message flow  500 . Thus, at step  702 , the femtocell device may receive, from a WCD, a registration request for wireless service. Preferably, the registration request contains a WCD identifier that identifies the WCD. In response to receiving the registration request, at step  704 , the femtocell device may determine that the WCD is served by the wireless coverage area, and the WCD identifier is in a whitelist for the extended handset service. At step  706 , in response to determining that the WCD identifier is in the whitelist, the femtocell device may register the WCD so that the WCD is eligible for the extended handset service, and transmit a registration confirm to the WCD. Then, at step  708 , in response to receiving an incoming call request seeking to establish a call to the WCD, the femtocell device may cause the telephony device to alert. 
     At some later point in time, the femtocell device may determine that the WCD is no longer served by the wireless coverage area. In response to making this determination, the femtocell device may de-register the WCD so that the WCD is not eligible for the extended handset service. 
     III. Additional Femtocell Device Features 
     In addition to the features described in reference to  FIGS. 4 ,  5 ,  6 , and  7 , a femtocell device may also support other features and functions that enhance its usefulness to users. 
     a. Automatic Whitelist Configuration 
     A femtocell device may be sold or leased by the same entity (i.e., a wireless service provider) that provides wireless service to WCDs. Thus, for example, if a family of four people, each person having their own WCD, decided to purchase a femtocell device for their residence, they will likely purchase it from the same wireless service provider to which their WCDs are subscribed. Thus, when the femtocell device is configured for operation in their residence, the femtocell device may register with the wireless service provider. In the process of this registration, or at some point thereafter, the wireless service provider may transmit the WCD identifiers of the family&#39;s four WCDs to the femtocell device. Then, the femtocell device may automatically provision these WCD identifiers in the femtocell device&#39;s whitelist. Thus, the four WCDs can be made automatically eligible for the extended handset service. 
     b. Redirect-on-Busy 
     When a WCD is registered for the extended handset service, incoming calls for the WCD may be routed to one or more telephony devices coupled to the femtocell device. Multiple telephone lines may be supported by the femtocell device (i.e., telephony interface  318  may contain more than one RJ11 jack, and each RJ11 jack may support an independent telephone line). If all of these lines are busy, or if the communications medium between the telephony interface and the telephony devices is at or near capacity, then incoming calls for the WCD might not be able to be routed to a telephony device without disrupting one or more calls already in progress. 
     In order to address this situation, a femtocell device may include logic to redirect such incoming calls back to the WCD when all telephone lines coupled to the femtocell device&#39;s telephony interface are busy. For example, at step  504  of message flow  500 , femtocell device  126  may determine that all telephone lines coupled to telephony interface  318  are busy. In response to making the determination, femtocell device  126  may transmit the incoming call request to WCD  302  via wireless interface  316 , rather than attempting to route the incoming call request to telephony device  306 . 
     c. Outgoing Calls Using a WCD Identifier 
     In addition to being able to receive incoming calls for a WCD at an attached telephony device, a femtocell device may be able to place outgoing calls from the telephony device such that these calls appear to be originating from the WCD. For example, each WCD eligible for the extended handset service (i.e., each WCD with its assigned WCD identifier in the whitelist) may be assigned a unique star code (e.g., “*22”) or some other type of telephony feature code. When a user of the telephony device dials a star code or feature code assigned to a given WCD identifier prior to dialing a destination number, the femtocell device may use the given WCD identifier as the calling party number, possibly in place of any number assigned to the telephony device. Thus, based on the use of the star code, the femtocell device may use the given WCD identifier when communicating with other devices on behalf of the WCD. As a result, it would appear to the called party, and possibly other network devices as well, that WCD initiated the call. 
     d. Both a WCD and a Telephony device Alerting 
     Upon receiving an incoming call request for a WCD that is eligible for the extended handset service, the femtocell device may cause a telephony device to alert instead of causing the WCD to alert. However, the femtocell device may alternatively cause both the telephony device and the WCD to alert. In this way, the user of the WCD can conveniently answer either the WCD or the telephony device. Once one of these devices is answered, the femtocell device preferably causes the other device to stop alerting. 
     IV. Conclusion 
     Example embodiments have been described above. Those skilled in the art will understand, however, that changes and modifications may be made to these embodiments without departing from the true scope and spirit of the invention, which is defined by the claims.