Method for automatic and seamless call transfers between a licensed wireless system and an unlicensed wireless system

A method of integrating a licensed wireless system and an unlicensed wireless system includes establishing a communication session through a landline. The communication session is linked to a subscriber device through an unlicensed wireless system servicing an unlicensed wireless system service area. An indication is received that the subscriber device is moving from the unlicensed wireless system service area into a licensed wireless system service area. Without disrupting the communication session, the communication session is automatically transitioned from the unlicensed wireless system to a licensed wireless system servicing the licensed wireless system service area. Similarly, a call initiated on the licensed wireless system is automatically transitioned to the unlicensed wireless system when the subscriber device enters the unlicensed wireless system service area.

BRIEF DESCRIPTION OF THE INVENTION

This invention relates generally to telecommunications. More particularly, this invention relates to a technique for seamlessly integrating voice and data telecommunication services across a licensed wireless system and an unlicensed wireless system.

BACKGROUND OF THE INVENTION

Licensed wireless systems provide mobile wireless communications to individuals using wireless transceivers. Licensed wireless systems refer to public cellular telephone systems and/or Personal Communication Services (PCS) telephone systems. Wireless transceivers include cellular telephones, PCS telephones, wireless-enabled personal digital assistants, wireless modems, and the like.

Licensed wireless systems utilize wireless signal frequencies that are licensed from governments. Large fees are paid for access to these frequencies. Expensive base station equipment is used to support communications on licensed frequencies. Base stations are typically installed approximately a mile apart from one another. As a result, the quality of service (voice quality and speed of data transfer) in wireless systems is considerably inferior to the quality of service afforded by landline (wired) connections. Thus, the user of a licensed wireless system pays relatively high fees for relatively low quality service.

Landline (wired) connections are extensively deployed and generally perform at a lower cost with higher quality voice and higher speed data services. The problem with landline connections is that they constrain the mobility of a user. Traditionally, a physical connection to the landline was required. Currently, unlicensed wireless communication systems are deployed to increase the mobility of an individual using a landline. The mobility range associated with such systems is typically on the order of 100 meters. A common unlicensed wireless communication system includes a base station with a physical connection to a landline. The base station has a RF transceiver to facilitate communication with a wireless handset that is operative within a modest distance of the base station. Thus, this option provides higher quality services at a lower cost, but the services only extend a modest distance from the base station.

Thus, there are significant shortcomings associated with current landline systems and licensed wireless systems. For this reason, individuals commonly have one telephone number for landline communications and one telephone number for licensed wireless communications. This leads to additional expense and inconvenience for an individual. It would be highly desirable if an individual could utilize a single telephone number for both landline communications and licensed wireless communications. Ideally, such a system would allow an individual, through seamless handoffs between the two systems, to exploit the benefits of each system.

SUMMARY OF THE INVENTION

A method of integrating a licensed wireless system and an unlicensed wireless system includes establishing a communication session through a landline. The communication session is linked to a subscriber device through an unlicensed wireless system servicing an unlicensed wireless system service area. An indication is received that the subscriber device is moving from the unlicensed wireless system service area into a licensed wireless system service area. Without disrupting the communication session, the communication session is automatically transitioned from the unlicensed wireless system to a licensed wireless system servicing the licensed wireless system service area. Similarly, a call initiated on the licensed wireless system is automatically transitioned to the unlicensed wireless system when the subscriber device enters the unlicensed wireless system service area.

Advantageously, services that would typically be provided via a licensed wireless system can be delivered to the unlicensed base station using inexpensive and high quality landline networks. The unlicensed base station subsequently provides service to a handset using unlicensed, free spectrum (e.g., spectrum around 2.4 GHz or 5 GHz). Thus, when a subscriber is within range of the unlicensed base station, the subscriber enjoys low cost, high speed, and high quality voice and data services. In addition, the subscriber enjoys extended service range since the handset can receive services deep within a building. This type of service range is not reliably provided by a licensed wireless system.

The invention also allows the subscriber to roam outside the range of the unlicensed base station without dropping communications. Instead, roaming outside the range of the unlicensed base station results in a seamless handoff (also referred to as a hand over) wherein communication services are automatically provided by the licensed wireless system.

While the invention provides advantages to the subscriber, the invention also provides advantages to the wireless system service provider. First, the unlicensed base stations are relatively low cost and therefore the wireless system service provider is in a position to extend services without incurring significant infrastructure expense. Further, the integration of the landline and wireless systems allows a single communication service provider to secure fee-paying accounts for both landline and wireless services. Finally, since the invention relies upon installed wireless system infrastructure for services such as authentication, expensive system upgrades are not required.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1illustrates a system10that may be operated in accordance with an embodiment of the present invention. The system10includes a subscriber device12, which is a wireless transceiver, such as a cellular telephone, a PCS telephone, a wireless data modem, a wireless enabled Personal Digital Assistant, a wireless enabled computer, and the like. This subscriber device12is in wireless electronic communication with a licensed wireless communication service that provides voice and/or data services. By way of example, the invention is disclosed in connection with a licensed wireless communication service in the form of a cellular network14. When the subscriber device12is within an unlicensed wireless service coverage area16, the licensed wireless service is substituted, without interruption, with an unlicensed wireless service that is facilitated through a base station18.

The base station18wirelessly transmits telephone signals from a standard Public Switched Telephone Network (PSTN)20and, if necessary, a standard Private Base eXchange (PBX)22, to a subscriber device12. Specifically, when a device12is within an unlicensed wireless service coverage area16, the originating base station18provides the device12with wireless telephone service originating from a PSTN20rather than a cellular network14. Since the PSTN20is used, the subscriber device12receives high quality voice or data services at a relatively low cost. If the user of the subscriber device12roams outside of the unlicensed wireless service coverage area16, the same communication session can be maintained without interruption by transitioning to the licensed wireless service provided by the cellular network14. Techniques for implementing seamless transitions of this type are discussed in detail below.

A system server24facilitates seamless transitions between the licensed wireless service and the unlicensed wireless service. The system server24is in electronic communication with the standard cellular network14. In one embodiment of the invention as shown inFIG. 1, the system server24is also in electronic communication with the base station18through a Local Area Network (LAN)28and a larger network30, such as the Internet. The system server24and the base station18may be linked through any number of communication services, including Digital Subscriber Line (DSL), cable, satellite, and the like.

FIG. 1illustrates that the cellular network14includes standard components, such as a cellular core network15, a Mobile Switching Center (MSC)26, Visitor Location Register (VLR)32, a Home Location Register (HLR)34, an Authentication Center (AC)38, and a Base Station Controller (BSC)38. As discussed below, these standard components are utilized in a novel manner in order to provide extended functionality for a subscriber device12.

FIG. 2illustrates a subscriber device12. As previously indicated, the subscriber device12may be a wireless telephone or a wireless modem. In the case of a wireless telephone, the subscriber device12includes a display100, keypad102, and a control circuit104. The display100may be used to provide a visual indication to a user when the subscriber device12is within the service range of the base station18. The keypad102is used in a conventional manner. The control circuit104may be in the form of a processor, a hardwired circuit, a programmable logic device, an application specific integrated circuit, and the like.

The control circuit104is also connected to a memory module106and, via audio switch108, to an audio input/output circuit109. Wireless signals in the unlicensed spectrum are received by an antenna110and are filtered by a filter112to improve signal clarity and/or strength. The wireless signals are then processed by unlicensed wireless circuitry114, which is also referred to as unlicensed wireless communication signal processing circuitry. The unlicensed wireless circuitry operates as a standard transceiver for processing unlicensed wireless signals. The circuitry114may support any number of unlicensed wireless standards. For example, currently in the U.S., unlicensed wireless signals may be sent at frequencies around 900 MHz, 2.4 GHz, or 5 GHz. Unlicensed wireless communication may be implemented in accordance with the invention utilizing any number of unlicensed spectrum communications protocols, including Bluetooth, IEEE 802.11a, IEEE 802.11b, and Hyper-LAN. Advantageously, many licensed wireless subscriber devices are currently being configured to include unlicensed wireless circuitry for such applications as remote microphones and speakers. In accordance with the invention, this circuitry is used for a new application, namely, communicating with a base station, as discussed below.

Selected signals, such as location update data or signal strength data, are sent to the control circuit104. Audio data is converted to an audio signal by audio circuitry116and is sent to an audio switch108for broadcast by an audio input/output circuit109. Audio signals transmitted to the audio input/output circuit109are transmitted by audio switch108to the control circuit104, which is capable of sending audio and other data to unlicensed wireless circuitry114. Unlicensed spectrum signals are then sent through the filter112and on to the antenna110, where they are broadcast to the base station18.

In similar manner, wireless signals from a licensed cellular network14are transmitted to the antenna111, filtered by the filter113, and are then processed by the licensed wireless circuitry118, also referred to as licensed wireless communication signal processing circuitry. These signals are subsequently converted to an audio signal by audio circuitry120or are processed by control circuit104. As above, signals originating from the device12can also be sent out, but here the destination is a licensed wireless communication network (e.g., cellular network14) rather than a base station18. In the event of a data modem, the audio input/output circuit109is omitted and a data source is applied directly to the control circuit104. Audio signals transmitted from the audio input109are transmitted by audio switch108to the control circuit104, which is capable of sending audio and other data to licensed wireless circuitry118. Wireless signals are then sent through the filter113to the antenna111, where they are broadcast to the licensed wireless network14.

The individual subscriber device components discussed up to this point are standard. The combination of these devices is believed to be novel, as is the operation of these devices in accordance with a set of executable programs stored in memory106. The executable programs within memory106are shown by way of example. The same functionality may be realized through hardwired circuits, application specific integrated circuits, programmable logic devices, and the like. Indeed, the various components of the subscriber device12may be combined or integrated in any number of ways. The embodiment ofFIG. 2is for the purpose of illustration.

The executable programs reside on top of standard licensed wireless system call processing software. In addition, the programs reside on top of standard unlicensed wireless link protocol software (e.g., standard Bluetooth or 802.11b software). The programs bridge these systems by exchanging messages between the separate software stacks. Advantageously, this approach allows a large portion of the existing software protocols in the subscriber device12to be reused without any changes.

The memory module106contains a location tracking module122that records the current location of the device12(i.e., whether the device is within an unlicensed coverage area16). In addition, the module106contains an authentication and authorization module124to coordinate an authentication procedure for validating that the device12is licensed for use within the unlicensed coverage area16. As discussed below, the invention utilizes the authentication infrastructure associated with the licensed wireless system to authenticate and authorize a subscriber device for unlicensed wireless system services. The memory106also includes a handoff module126to coordinate seamless service exchanges between a base station18supporting unlicensed wireless communications and a licensed wireless communications network, such as a cellular network14. The operations associated with each of the modules stored in memory106are discussed in further detail below.

FIG. 3illustrates an embodiment of a base station18in accordance with an embodiment of the present invention. When the subscriber device12is within the coverage area16of the base station18, the base station18can be used to provide the subscriber device12with landline quality data and voice service via an unlicensed wireless communication link. In particular, the base station18interconnects to the existing telephone network to provide a final link to a subscriber device12through a short-range two-way radio link.

In one embodiment of the invention, the base station18is controlled by a control circuit200, which is in communication with the LAN28and therefore the system server24via router jack202and/or Ethernet jack204. The control circuit200may be a processor, a hardwired circuit, a programmable logic device, an application specific integrated circuit and the like. Signals from the system server24travel through one of these jacks into network interface circuitry206and on to the control circuit200. This allows the base station18to communicate with the system server24. As discussed below, the server24determines whether and when to route phone service over the unlicensed wireless system (e.g., via the PSTN20and base station18) or the licensed wireless system (e.g., via cellular network14).

The control circuit200is also in communication with a landline (PSTN20and, in the typical business context, PBX22) via a phone line jack208and/or phone extension jack210. These jacks transmit information between the PSTN20and control circuit200through Plain Old Telephone Service (POTS) interface circuitry212. Audio data is translated by audio circuitry214, while other data can be directly exchanged with the control circuit200.

The base station18communicates wirelessly with devices12using a radio frequency circuit216. This circuit216includes standard circuitry to receive and transmit electronic voice and/or data in an unlicensed wireless signal format. For example, currently in the U.S., unlicensed wireless signals may be sent in the frequency range between 2.4 GHz and 5 GHz. Unlicensed wireless communication may be implemented in accordance with the invention utilizing any number of unlicensed spectrum communications protocols, including Bluetooth, IEEE 802.11a, IEEE 802.11b, and Hyper-LAN.

A typical circuit216consists of transmission circuitry218for transmitting signals to a device12, receiving circuitry220for receiving signals from the device12, and base band circuitry222. The baseband circuitry222contains standard circuitry for down converting unlicensed wireless signals to base band signals, which allows for the extraction of relevant information by the control circuit200. The base band circuitry222also contains standard circuitry for up converting base band data from the control circuit200to unlicensed wireless signals for broadcast by transmission circuitry218.

The control circuit200is also connected to a memory module224. The memory module224contains a provisioning module226that is used to facilitate the initial configuration and servicing of the base station18and subscriber device12. The module224also includes a subscriber interface module228. The subscriber interface module228instructs the control circuit200to periodically broadcast a signal (e.g., an unlicensed wireless communication base station identification signal). If a subscriber device12responds to the signal, then the base station18knows that the subscriber device12is within the unlicensed coverage area16. The module224also contains an authentication module230to coordinate the authentication of a subscriber device12that has entered the unlicensed coverage area16. In one embodiment of the invention, the memory224includes an enhanced service module232. The enhanced service module may be used to provide improved services to a subscriber device. For example, if the user of a subscriber device is playing a low latency on-line game, different screen displays can be cached in the base station18and then be quickly downloaded to the subscriber device12. Each of the modules stored in memory224can also be implemented as hardwired circuits, application specific integrated circuits, programmable logic devices, and the like.

The enhanced service module232may also be used to implement other advanced features. For example, the enhanced service module232can be configured to append a set of prefix digits before dialed digits to instruct the server24to route long distance calls on a specific service provider network.

The enhanced service module232can also be used to simultaneously support multiple subscribers. For example, the base station18may support multiple subscriber devices through a single or multiple landline connections.

Preferably, the subscriber interface module228of the base station18is configured to advise a subscriber device when the landline associated with the base station18is occupied. In such a case, the handoff module126of the subscriber device will no longer attempt to make contact with the base station18, but will continue to utilize the licensed wireless system for call servicing.

In order to provide landline-quality service to subscriber devices12, a base station18is installed directly in the path of a typical phone system.FIG. 4Aillustrates a typical office or workplace, where a telephone300is connected to a PBX22. The PBX22is installed between the telephone300and PSTN20to provide a private telephone network in which a number of telephones300share a certain number of outside lines from the PSTN20.FIG. 4Aillustrates that a Personal Computer (PC)302can be connected to the LAN28for communication with the Internet30.

FIG. 4Billustrates the workplace environment ofFIG. 4Amodified to incorporate the base station18of the invention. The base station18is placed in electronic communication with both the telephone300(e.g., via phone line jack208) and the LAN28(e.g., via Ethernet jack204). This configuration allows base station18to receive landline voice and data from a PSTN20and broadcast it to subscriber devices12when they are within the coverage area16. The base station18is also-connected to a LAN28, which allows it to communicate with the system server24in order to coordinate handoffs between the licensed wireless and unlicensed wireless systems. Advantageously, the base station18operates transparently with respect to the PBX22, the LAN28, the telephone300, and the PC302. In the event that the PBX22is Internet Protocol based, the base station18can be connected solely to the LAN28.

FIG. 4Cillustrates a typical home setting, which is usually similar to the workplace setting ofFIG. 4Aminus the LAN28and PBX22. The telephone300is ordinarily connected directly with Plain Old Telephone Service (POTS)304, which is simply another term for PSTN20. Connection to the Internet30is provided by a modem306in communication with a PC302.FIG. 4Dillustrates the placement of base station18within this typical home setting. Here, the base station18is placed in electronic communication with both a telephone300and modem306, allowing it to communicate directly with the POTS304/PSTN20and, through modem306, with the Internet30and system server24. Once again, the base station18operates transparently with respect to the modem306, the POTS304, the telephone300, and the PC302.

In both the workplace and home settings, the base station18can be in simultaneous communication with both a telephone landline and a system server24. When a subscriber device12roams inside the coverage area16, the base station18can thus provide landline-quality service to device12. The invention should thus be construed to include an apparatus and method for the seamless switching of telephone service between a cellular network14and a landline-based base station18that can be used in either a residential or commercial setting.

As mentioned above, for purposes of this invention a landline can be interchangeably referred to as a POTS304or PSTN20. However, the invention should not be construed as limited to simply the POTS or PSTN context. Rather, the invention discloses a base station18that can provide landline-quality service to a subscriber device12by communicating with any landline network. Examples of such networks include, but are not limited to, DSL, cable or cable modem networks.

FIG. 5illustrates a system server24, which manages the mobility of subscriber devices12between a landline-based unlicensed wireless service from a base station18and a licensed wireless service, such as from a cellular network14. A typical system server24is controlled by a central processing unit (CPU)400, which is connected to a bus401. Network interface cards402(e.g., Ethernet cards) for communicating with the Internet30are also connected to the bus401. Licensed network interface cards404(e.g., SS7 cards) for communicating with cellular networks14are also connected to the bus401. This allows the system server24to use Internet Protocol (IP) and/or SS7 protocol and/or MAP & IS-41 protocols to connect to the Internet and cellular core networks.

The system server24also contains a memory module406that stores a number of programs, databases and other assorted modules. More specifically, the module406contains signaling control programs408. The signaling control programs408are standard programs for establishing communications with the licensed wireless network. Therefore, for example, the signaling control programs408may include a Transaction Capability Application Part (TCAP) module, a Message Transfer Part (MTP) module, and an Interim Standard (IS41) module to support Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). Memory46may also store datapath control programs410. By way of example, the datapath control programs may include standard programs to facilitate computer network data transfers. By way of example, the datapath control programs may include an Internet Protocol (IP) module and a Gateway Tunnel Protocol (GTP) module.

The memory406also stores various system server application programs412. These application programs include system bridge programs414for handling transitions in service from licensed to unlicensed wireless services and vice versa. The memory406also stores a location database416for storing the current location of devices12and indicating whether they are within the coverage area16. Also included is a billing module418for recording usage statistics for billing purposes. The billing module418distinguishes between charges for licensed wireless services and unlicensed wireless services. A provisioning module420is included to facilitate the installation of new base stations. An authentication module422is used to facilitate the authentication of a subscriber device within an unlicensed wireless service area. As discussed below, the authentication module422includes data and executable instructions to emulate certain components of a licensed wireless network. For example, the authentication module emulates a mobile switching center during the authentication process.

The major components of the invention—the subscriber device12, the base station18, and the system server24—have now been described. The operations of these devices are more fully appreciated with the following discussion.

The invention's facilitation of seamless transitions between licensed and unlicensed wireless services is more fully appreciated in connection withFIG. 6. Base station18broadcasts within a set of boundaries B1, B2, B3and B4. A subscriber device12located outside these boundaries is serviced by a licensed wireless system, such as a standard cellular network14. However, once the device12crosses boundary B3, the handoff from the licensed wireless service to the unlicensed wireless service begins. That is, at the B3boundary the base station18is able to recognize the presence of the subscriber device12. As previously indicated, the base station18includes a subscriber interface module228that coordinates the transmission of a service range signal that is identified by a subscriber device12. That is, the location tracking module122of the subscriber device12is used to coordinate the identification of a base station signal. In the presence of such a signal, the location tracking module122coordinates the transmittal of an acknowledgment signal to the base station18.

Preferably, the subscriber interface module228of the base station18identifies the boundary points of the service area16by using the received signal strength and the transmit-power level setting from the subscriber device12. In particular, an automated process is preferably used to learn the boundary distances through heuristically measuring the success rate and adjusting the boundary distance for optimal handoff success rates.

In one embodiment, the location tracking module122of the subscriber device12is implemented to periodically wake the unlicensed wireless circuitry114to sniff and thereby determine whether it is within the range of a base station. If so, the subscriber device registers with the base station18, if not, the unlicensed wireless circuitry114is activated at a later time.

Under the control of the subscriber interface module228, the base station18identifies the acknowledgement signal and transmits a subscriber device present signal to the router jack202, the Ethernet jack204, the phone line jack208, or the phone extension jack210. The subscriber device present signal is subsequently directed through a network (e.g., the LAN28and Internet30) to the system server24, which notes that the subscriber device12is now within the service area of the base station18. In particular, the system server24logs this information in the location database416.

Once the system server24logs the fact that the subscriber device12is within the service range of the base station18, it contacts the cellular network14to initiate a call to the landline associated with the base station18. It is known in the art to utilize a cellular network14to establish a call to a landline number. For example,FIG. 1illustrates a link between the Mobile Switch Center (MSC)26and the PSTN22. In the prior art, this feature is used to direct a call intended for a mobile device to a landline telephone when the user of the mobile device has advised the cellular system that the landline telephone can be used to receive calls. Observe in this situation that the transition from the cellular network to the landline telephone is established prior to the call being placed. This prior art scenario stands in sharp contrast to the present invention where during the course of an already established communication session control is transferred from a licensed wireless service to an unlicensed wireless service or vice versa. This aspect of the invention is more fully appreciated in connection with the following discussion.

As previously indicated, when the subscriber device12crosses the boundary B3, a landline call to or from the base station18is initiated. Once the landline call is received at the base station18, the base station18begins transmitting to the subscriber device12using the unlicensed wireless spectrum. These transmissions are processed by the unlicensed wireless circuitry114of the subscriber device12(SeeFIG. 2). At this point, the licensed wireless circuitry118is also active and the audio switch108is responsive to the licensed wireless circuitry118. Thus, the subscriber device12is processing both licensed wireless signals and unlicensed wireless signals at this point. The handoff module126can coordinate this operation.

The subscriber interface module228of the base station18continues to monitor the signal strength from the subscriber device12. When the signal strength reaches a threshold corresponding to the crossing of boundary B4, the subscriber interface module228initiates a handoff command, which is applied to the RF circuit216. The handoff command is received at the subscriber device12and is processed by the handoff module126, which generates a handoff signal that is applied to the audio switch108. The handoff signal causes the audio switch108to process information from the audio circuitry116associated with the unlicensed wireless circuitry114.

At this point, the licensed wireless circuitry118can be turned off. The ability to turn this circuitry off is a significant advantage because it preserves battery life. Typically, the licensed wireless circuitry remains active in order to provide location information to the licensed wireless system infrastructure. However, as discussed below, this location information is available in accordance with the invention. Therefore, the licensed wireless circuitry can be shut down to obtain a significant extension in battery life. Alternately, the licensed wireless circuitry118can remain in a low power state to receive signaling or messages from the licensed wireless system, while voice is carried over the unlicensed system.

The spacing between boundaries B3and B4allows time for the establishment of connections between the subscriber device12and both the licensed network and unlicensed network. This allows for the immediate switching of service to the unlicensed network once the subscriber device12crosses boundary B4, thus creating a seamless transition to base station service that is transparent to the user.

Once the device12is within boundary B4, service is originated within the PSTN20and broadcast wirelessly to the device12by the base station18. If the device12travels away from this base station18, service is handed off from the base station18to a licensed wireless network14in a manner similar to the process described above. Specifically, once the device12crosses boundary B2, a simultaneous link is established with a licensed wireless network (e.g., cellular network14). When the device12further crosses boundary B1, a seamless handoff is made from the unlicensed wireless service originating over the PSTN20to the licensed wireless network (e.g., cellular network14). At this point, the subscriber device12receives wireless services from the cellular network14in a standard manner.

FIG. 7provides a more detailed characterization of this handoff process from an unlicensed wireless service to a licensed wireless service. When the subscriber device12is within the service area16of the base station18, the subscriber device12transmits to the base station18information on the signal strengths of the frequencies of the nearby licensed wireless base stations. The base station18forwards this information to the system server24, which in turn sends the information to the Visitor Location Register (VLR)32. This operation is shown with arrow450inFIG. 7.

In response to this message, the licensed wireless system provides the parameters that are needed when the subscriber device12needs a handoff from the unlicensed wireless system to the licensed wireless system. This information includes the identity of the base station to which the handoff should be made. By way of example, in a GSM cellular system, these parameters are CI (Cell Identity) and LAC (Location Area Code). This handoff information may be obtained and stored in the base station18before a call is made or when a call is made. In any event, the handoff information can be secured well before the subscriber device12roams outside the coverage area of the base station18. The availability of this information allows the subscriber device12to quickly transition to the licensed wireless system. In addition, this information allows the licensed wireless circuitry118to be shut down for the purpose of extending battery life.

The licensed wireless system connection information may be delivered to the base station18via a landline connection as shown with line452. Alternately, the information may be delivered through a communication session between the system server24and the mobile switch center26and then the system server24and the base station18, as shown with arrows454and456.

As shown with arrow458inFIG. 7, the base station18continuously makes power measurements of signals that are received from the subscriber device12. When the power measurements begin to grow weak, the base station may notify the system server24to initiate a handoff to the licensed wireless system. In turn, the system server24may advise the Mobile Switch Center (MSC)26of the hand over candidate, as shown with arrows460and462.

When the power measurements at the base station18become sufficiently weak, indicating that the subscriber device12is moving away from the base station18(e.g., crossing boundary B2) a formal hand over request is initiated. In particular, the base station18transmits to the system server24the base station identity (e.g., CI, LAC, etc.) to which the handoff should be transferred, as shown with arrow458. The system server24contacts the MSC26to initiate a handoff, as shown with arrow460. The MSC26contacts the Base Station Controller (BSC)38, as shown with arrow462. In response, the BSC38generates a channel number, a slot number and a handoff reference. As shown with arrow464, this information is passed to the Base Station Transceiver System (BTS)500. The information is also passed back to the subscriber device12through the MSC26, the system server24, and the base station18, as shown with arrows466,468,470, and472.

In response to this information, the BTS500turns on a transmitter and receiver at the specified channel number and slot number. Similarly, the subscriber device12turns on its transceiver circuitry118. The BTS500seeks a response from the subscriber device with a matching reference number, as shown with arrow474. Once the subscriber device12receives the BTS transmission, it sends a message to the BTS with the handoff reference, as shown with arrow476. At this point, a new licensed wireless link is established on the given channel and slot number, as shown with arrow478. Once the licensed wireless link is established, the unlicensed wireless link is turned off, as shown with line480inFIG. 7. Thereafter, the BTS500, the BSC38, and the MSC26operate in a standard manner to supply licensed wireless services to the subscriber device12. The foregoing operations may be implemented using the handoff module126of the subscriber device12, the subscriber interface module228of the base station18, and the system bridge programs414of the system server24.

As previously indicated, a handoff from a licensed wireless service to an unlicensed wireless service occurs in a similar but reverse fashion. When the subscriber devices12cross boundary B3from a remote location the base station18initiates a handoff operation by sending a request to the system server24, which conveys the request to the MSC26. The MSC26then hands off the call to the landline number assigned to the base station18.

Between boundaries B3and B4, both the licensed wireless (e.g., cellular) link and unlicensed wireless (e.g., landline originated) link are simultaneously active. After a period in which both links are simultaneously active, control of the communication session is switched from the licensed wireless circuitry118to the unlicensed wireless circuitry114. The handoff module126may coordinate this handoff in response to a handoff command initiated at the subscriber interface module228of the base station18. As above, the maintenance of simultaneous licensed and unlicensed wireless links for a period of time ensures a successful seamless handoff. This reduces the number of dropped calls, and allows for successful handoffs even when the signaling messages among different elements of the cellular and landline-based systems experience delays or latency.

The foregoing discussion was directed toward handoffs between licensed wireless services and unlicensed wireless services. The invention also includes a technique for seamless handoffs between unlicensed wireless service base stations. Such a technique would be valuable, for example, in the case where an office building has a large number of base stations18to supply unlicensed wireless services to a user that would otherwise receive poor quality licensed wireless service within the office building.

Thus, the invention includes a system wherein a plurality of base stations18exist with overlapping coverage areas16. This allows a subscriber device12to roam freely among the coverage areas16.

FIG. 8illustrates such a system. The subscriber device12is registered with base stations18-1and18-2. Base stations18-1and18-2communicate with each other using LAN28. The base stations18-1and18-2are shown installed in a typical workplace setting, with telephones300and PCs302connected to a LAN28and PBX22in a standard fashion. Note that the coverage areas604and606of the base stations18-2and18-2overlap. As a device12moves from one area604to another area606, voice and data signals from the first base station18-1are seamlessly handed off to the second base station18-2.

Periodically, the base stations18-1and18-2broadcast a message over the LAN28to all other base stations connected to the LAN28. This message includes a time stamp, a signal indicating the particular base station, the subscriber number, and a range number indicating the distance between that base station and the device12. A separate message is broadcast for each base station on the LAN28. A range number can be calculated by relying upon the ability of the base station18to measure the signal strengths emitted from the subscriber device or vice versa.

In accordance with this feature of the invention, there is no centralized control mechanism for handling handoffs. Instead, the subscriber interface module228of each base station18is used to coordinate handoffs between base stations based upon signal strengths and/or range numbers. For example, inFIG. 8, at position T1the base station18-1would transmit a time stamp, a base station number, a subscriber number, and a range number indicating that the subscriber device12is relatively close to the base station18-1. At T2the base station18-1would transmit the same information except a different range number indicating that the signal between the base station18-1and the subscriber device12is weaker. By position T3, the base station18-2would send a signal on the LAN28indicating that it has a range number indicating that the subscriber device12is now closer to it than to base station18-1. Accordingly, both base stations would recognize that a transition from base station18-1to base station18-2should transpire. Under these circumstances, the second base station18-2transmits a signal over LAN28to the first base station18-1requesting a transition. Once the first base station18-1acknowledges this request, it forwards the call to the second base station18-2and service is continued without disruption. For example, the call may be forwarded over LAN28using Voice Over Internet Protocol (VOIP) techniques.

The discussion up to this point has been directed toward seamless transitions between licensed and unlicensed wireless services. Attention now turns to other aspects of the invention. Another aspect of the invention is a technique for assigning a base station to a landline telephone number. Another aspect of the invention is a technique for authenticating a user for unlicensed wireless services. Advantageously, authentication is implemented through reliance upon existing authentication infrastructure associated with the licensed wireless network. Thus, a separate authentication scheme need not be implemented. Another aspect of the invention that is discussed below is the provisioning of a base station into the overall licensed wireless network. As discussed below, the provisioning operation is automatically performed and therefore does not require technical sophistication or expertise on behalf of the user.

FIG. 9illustrates a technique for assigning a landline number to a base station18. Upon installation and power-up, the base station18queries the subscriber device12for the local landline phone number to which the base station is connected. In some embodiments, the base station12will also solicit the Internet Protocol (IP) address for the system server24. After the user enters the phone number and/or IP address into the subscriber device12, the information is transmitted to the base station18, as shown with arrow610ofFIG. 9. The base station18forwards the same information to the system server24, as shown with arrow612. The system server24then transmits this information for storage in the HLR34, as shown with arrow614. Once stored in the HLR34, the MSC26can access the number as a mobile system roaming number (MSRN), as shown with arrows616and618. Thereafter, the mobile system roaming number can be used in a conventional manner to route a call to the base station18. Alternately, the MSRN may be a number corresponding to a number associated with the system server24. In which case, the system server24sends the call to the base station18.

Another aspect of the invention is authentication. As previously indicated, the invention utilizes the authentication infrastructure associated with the licensed wireless network to authenticate users for the unlicensed wireless network.

FIG. 10illustrates a licensed wireless system authentication process utilized in accordance with the prior art. In this example, the subscriber device12moves from the coverage area served by its home MSC (referred to as MSC-A) to the coverage area served by MSC-B. As soon as the subscriber device12enters a cell that is served by MSC-B, it registered with the system by sending an authentication request and a location update to Base Station System (BSS)600, as shown with arrow650. The location update request includes an international mobile subscriber identity (IMSI).

BSS600forwards this information to the VLR32associated with MSC-B, as shown with arrow652. The VLR of MSC-B in turn sends a message to the VLR and HLR of the SMC-A, as shown with arrows654and656. This information serves as a request for authentication of the subscriber device12as well as to inform the HLR34of the current location of the subscriber device12as served by the MSC-B. The authentication is performed as follows.

The authentication center (AuC)36generates a parameter called SRES (signed response). In order to generate the SRES, it uses an authentication algorithm A3, such as a public key/private key algorithm. The algorithm A3processes a secret key Ki, a random number RAND, and the IMSI to produce the SRES. The IMSI, RAND, and SRES are passed to the MSC-A (arrow658) and MSC-B (arrow660). The SRES is temporarily stored at the MSC-B until the authentication operation is completed. The MSC-B passes the IMSI and the RAND to the BSS, which passes the information to the subscriber device12. Based upon the IMSI and the RAND that it receives (referred to herein as licensed wireless communication system security information), along with the secret key Ki that it stores, the subscriber device12executes the same authentication algorithm A3. This results in the subscriber device12producing a SRES, which is referred to as an authentication result. If the subscriber device is legitimate, it has the same secret key Ki encoded in it as the one in the HLR. The service provider encodes this key at the time of activating the subscriber. This key is known only to the subscriber device and to the HLR.

The SRES, or authentication result, generated by the subscriber device12is passed with the IMSI to the BSS-B (arrow666), which passes it to the MSC-B (arrow668). The MSC-B compares the SRES generated by the subscriber device12to the SRES generated by the HLR. Authentication is only successful if the two numbers match. The SRES generated by the HLR can be referred to as an authentication value. If the authentication value from the HLR matches the authentication result from the subscriber device12, then an authentication command is generated.

The above process assists in understanding the authentication process included in the present invention, as the new method is designed to utilize the existing authentication process already existent in the licensed wireless system.FIG. 11illustrates an authentication process in accordance with the present invention. In accordance with the invention, the base station18is designed to emulate a BSS600, and the system server24is designed to emulate an MSC26.

When the subscriber device12enters the service area of the base station18, it registers with the base station. The authentication module124of the subscriber device12subsequently intercepts the registration message that is typically sent to the licensed wireless base station (e.g., BSS600). This information, referred to as a licensed wireless authentication request, is sent to the base station18, as shown with arrow680. The base station18, at the direction of the authentication module230, routes the information to the system server24. In particular, the authentication module230of the base station18forms an Internet Protocol (IP) packet containing the information and routes it to the system server24. As shown with arrow684, the system server24forwards the information to the MSC-A. The authentication module422of the system server24may be used for this purpose. In this capacity, the authentication module44assists the system server24in its operation of emulating a VLR. The operations at arrows656,658, and660are identical to the operations performed in the prior art system ofFIG. 10.

At this point, the system server24stores the SRES, instead of an MSC. The system server24forwards the IMSI and RAND information to the base station18, as shown with arrow686. The base station18, emulating a BSS, passes this information to the subscriber device12. The authentication operation performed at the subscriber device is conventional, with the subscriber device returning an authentication result (e.g., an IMSI and a SRES) to the base station18, as shown with arrow690. The base station18passes this information to the system server24, as shown with arrow692. The system server24then checks for an SRES match. That is, the system server compares the authentication result produced by the subscriber device12to the authentication value (e.g., SRES) received from the MSC-A. Recall that this operation was performed by the MSC26in the prior art system ofFIG. 10. In the event of a match between the computed SRES values, an authentication command is produced and unlicensed wireless services may be delivered to the subscriber device12through the base station18.

Preferably, authentication is not performed every time the subscriber device registers with the base station18. Instead, the authentication module230of the base station18preferably stores previous authentication information and locally re-authenticates without accessing the system server24. This implementation is faster and otherwise reduces network traffic.

Yet another aspect of the invention involves provisioning of a base station in order to facilitate the licensed-to-unlicensed wireless communications achieved in accordance with the invention. By way of overview, the provisioning operation of the invention entails the base station18automatically configuring itself. In one embodiment, provisioning is accomplished by initially accessing a provisioning server. Subsequently, the base station registers with the system server. In the event that Internet access is available to the base station, the base station uses the Internet to access the provisioning server and the system server. If Internet access is not available, a Short Message Service Center may be used during the provisioning operation.

FIG. 12illustrates equipment utilized during the provisioning operation. In particular, the figure illustrates a subscriber device12and a base station18. In one embodiment, the base station18uses the Internet30to access a provisioning server700. For example, the base station18may access the Internet through a broadband modem, such as DSL. The provisioning server700supplies a service profile to the system server24, as discussed more fully below. In another embodiment of the invention, the base station18is provisioned through a wireless connection. In particular, a wireless link is established using a Short Messaging Service or packet data services supported by the cellular system. For example, a short messaging service message can be sent from the base station18to the subscriber device12, which then delivers the message to the BSS600. The BSS600delivers the message to the cellular network14, which delivers the message to the MSC26. The MSC26routes the message to the Short Message Service Center (SMSC)702, which routes the message over the Internet30to the provisioning server700. Information from the provisioning server700is delivered to the system server24and the base station18through a reverse path.

FIG. 13illustrates the process steps involved when the system ofFIG. 12carries out the provisioning process. The process is typically initiated upon installation and activation of a new base station18, and will be discussed in that context, but those of skill in the art will see that it can be performed any time that provisioning information must be updated.

When a base station18is initially powered up it contacts the provisioning server700(step800). The provisioning module226of the base station18coordinates this operation. In one embodiment, contact is made through the Internet30using one or more preprogrammed IP addresses for the provisioning server. Alternately, the provisioning server may be accessed through the SMSC, as discussed above. The base station18then identifies itself to the provisioning server700, for example, using a code preprogrammed at the time of manufacture. If the provisioning server700does not recognize the base station, the base station preferably provides an error indication. If the provisioning server700recognizes the base station, that processing proceeds to block806.

At this point, the base station broadcasts a signal to the subscriber device12instructing it to define itself (block806). For example, the subscriber device12may define itself by sending to the base station18an electronic serial number or a portion of an electronic serial number. This defining information is used to establish an association between the base station18and the subscribe device12. This local association is mapped with a local authentication procedure. Thereafter, whenever the subscriber device and the base station come into contact, they identify each other by passing the local authentication procedure. The two devices can only communicate if the local authentication procedure is successful.

The provisioning module127of the subscriber device12prompts the user to enter the landline telephone number associated with the base station18(block808). This information is then passed to the base station18. The base station then delivers information to the provisioning server (block810). For example, the base station will typically deliver the landline telephone number and a base station identification number to the provisioning server. The provisioning server then downloads a service profile to the base station and the system server (block812). The service profile can include the landline telephone number and caller services, such as call waiting, caller identification, and the like. The service profile may also include an IP address for the base station. The IP address allows packet data to be delivered to the base station. The service profile also includes the IP address of a system server24assigned to the base station18. Typically, the system server24is selected based upon proximity to the base station, as derived from the area code associated with the landline telephone number.

Observe that the provisioning server operates as a central registration point for all devices within the system. This central point makes it easier to modify system wide services. In addition, the provisioning server provides the benefit that a single address is programmed into each base station.

The base station takes the IP address of the system server from the service profile and contacts the system server (block814). If the service profiles match, an association is established between the system server, the base station, and the subscriber device. The system server subsequently updates the HLR of the subscriber device with contents of the service profile (block816). At this point, the authentication process ofFIG. 11would typically be performed. This provisioning process can be repeated whenever a new device12or base station18is introduced into the system.

Another aspect of the invention allows licensed wireless service users to seamlessly change between a desktop phone and a subscriber device12during a call, thus allowing them to use the most comfortable device at a given time. Thus, when a subscriber device12is located within a coverage area16, a user can simply pick up the desktop phone and continue their conversation. The subscriber device12can then be disconnected without any interruption in service. In this embodiment, the desktop phone and the base station are connected to the same landline, thereby providing this interchangeability. Likewise, when a caller is using a desktop phone within an area16, he or she can activate a subscriber device12and continue a call from there. In this instance, a button on the subscriber device is used to initiate communication with the base station that is connected to same landline. Subsequently hanging up the desktop phone will not interrupt service. Observe in this context that when the subscriber device is within the coverage area16of the base station18, both the subscriber device12and a desktop telephone may simultaneously ring in response to a call. The user can then pick up either device.