Abstract:
Methods and apparatus are disclosed for reducing wireless telecommunication costs for enterprises having a plurality of PBX-equipped sites, connected by either a public network (e.g., the PSTN, the Internet, etc.), a private network (e.g., leased lines, a virtual private network [VPN] over the Internet, etc.), or some combination of public and private networks. In particular, the illustrative embodiments of the present invention attempt to reduce telecommunication costs by advantageously routing calls from an off-premises wireless terminal belonging to the enterprise via one or more of the enterprise&#39;s private branch exchanges. The present invention is especially advantageous in that it can reduce telecommunication costs for calls from an off-premises wireless terminal to any type of destination: another cell phone, a wireline terminal, a private branch exchange, etc.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/854,440, filed Sep. 12, 2007, which is a continuation-in-part of U.S. patent application Ser. No. 11/780,127, filed 19 Jul. 2007, now U.S. Pat. No. 7,885,399, issued Feb. 8, 2011, entitled “Cost-Conscious Telecommunications Terminal”, which is incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to telecommunications in general, and, more particularly, to reducing wireless communications costs for enterprises. 
     BACKGROUND OF THE INVENTION 
     An organization that desires to provide employees at one location with telephones has, in general, two options. First, the organization can acquire one telephone and one telephone line per employee from the telephone company. Second, the organization can acquire one telephone per employee, a small number of telephone lines from the telephone company, and a piece of equipment that enables the employee&#39;s telephones to share the small number of telephone lines. In general, the second option is substantially less expensive than the first option, and the piece of equipment that enables the employees&#39; telephones to share the small number of telephone lines is called a “private-branch exchange” or “PBX.” In addition, private-branch exchanges typically provide a variety of useful telecommunications features to their users, such as call forwarding, three-way conferencing, and so forth. 
       FIG. 1  depicts a schematic diagram of telecommunications system  100  in the prior art. Telecommunications system  100  comprises affiliated off-premises telecommunications terminals  101 - 1  through  101 -X, wherein X is a positive integer; unaffiliated off-premises telecommunications terminal  102 ; affiliated on-premises telecommunications terminals  103 - 1  through  103 -X; private branch exchange telephone system  104 ; and telecommunications network  105 , interconnected as shown. 
     The terms “affiliated” and “unaffiliated,” as they apply to the off-premises terminals, refer to whether an off-premises terminal is affiliated with an on-premises terminal (i.e., a terminal served by private branch exchange  104 ). The relationship of an on-premises terminal (e.g., terminal  103 - 1 , etc.) with an affiliated off-premises terminal (e.g., terminal  101 - 1 , etc.) is described below and with respect to  FIG. 2 , with regards to extending a received call to one or both terminals. 
     Private branch exchange  104  is capable of switching incoming calls from telecommunications network  105  (e.g., the Public Switched Telephone Network, etc.) via one or more transmission lines to any of on-premises terminals  103 - 1  through  103 -N. Private branch exchange  104  is also capable of handling outgoing calls from any of on-premises terminals  103 - 1  through  103 -N to telecommunications network  105  via one or more transmission lines that connect private branch exchange  104  to telecommunications network  105 . 
     Private branch exchange  104  is capable of also extending an incoming call to a telephone number in telecommunications network  105 , in addition to switching the incoming call to on-premises terminal  103 -n, wherein n is an integer between 1 and N, inclusive. The telephone number that is extended-to in telecommunications network  105  corresponds to an affiliated terminal  101 -n. 
       FIG. 1  also depicts the address spaces that are relevant to telecommunications network  100  in the prior art. The term “address space” refers to an addressable region of telephone service. Address space  111  represents the addressable region served by telecommunications network  105 . Address space  112  represents the addressable region served by private branch exchange  104 . 
     Private branch exchange  104  acts as a “bridge” between address space  111  and address space  112 . When a calling party places a call to someone served by private branch exchange  104 , the calling party uses a dialing sequence that includes a telephone number that belongs to telecommunications network  105  and residing in address space  111 . As part of the dialing sequence, the calling party also uses an extension number that allows access to one of the on-premises telecommunications terminals that reside within address space  112 . 
     Thus an on premises telephone number is one that exists within the address space of the private branch exchange, and an off-premises telephone number is one that exists within the address space of the Public Switched Telephone Network. 
     Some private branch exchanges enable the user of an on-premises terminal to associate an off-premises terminal&#39;s telephone number (e.g., the user&#39;s cell phone number, etc.) with the on-premises terminal&#39;s telephone number for features such as automatic call forwarding. In such instances the off-premises terminal&#39;s telephone number is said to be mapped to the on-premises terminal&#39;s telephone number. Typically a private branch exchange that provides such a mapping feature stores the mappings in a table, such as the one shown in  FIG. 2 . 
     When an enterprise user&#39;s on-premises terminal is affiliated with his off-premises wireless terminal, the enterprise user can seamlessly and transparently:
         place calls from his wireless terminal that appear to originate from his on-premises terminal;   receive calls that are directed to his on-premises terminal on his wireless terminal; and   access all of the features of the enterprise&#39;s private branch exchange from his wireless terminal
 
from anywhere in the world. While these capabilities enable unprecedented worker mobility, they also can result in huge international roaming costs for global enterprises.
       

     SUMMARY OF THE INVENTION 
     The present invention overcomes some of the disadvantages of the prior art by potentially reducing wireless telecommunication costs for enterprises that have a plurality of PBX-equipped sites, connected by either a public network (e.g., the PSTN, the Internet, etc.), a private network (e.g., leased lines, a virtual private network [VPN] over the Internet, etc.), or some combination of public and private networks. In particular, the illustrative embodiments of the present invention attempt to reduce telecommunication costs by advantageously routing calls from an affiliated off-premises wireless terminal (e.g., cell phone, etc.) to its destination via one or more of the enterprise&#39;s private branch exchanges. The present invention is especially advantageous in that it can reduce telecommunication costs for calls from an off-premises wireless terminal to any type of destination: another cell phone, a wireline terminal, a private branch exchange, and so forth. Some illustrative scenarios include:
         an employee who is on business travel in the UK might call a supplier in Taiwan;   an employee who is on business travel in St. Louis might call a customer in New Jersey; or   an employee who is at a restaurant near his or her office in New York might call a fellow employee in San Francisco.       

     In accordance with the illustrative embodiments of the present invention, changes in the geo-location of an off-premises affiliated wireless terminal (e.g., cell phone, etc.) are tracked via a registration process, and the enterprise private branch exchange that is “closest” to the cell phone (i.e., that can communicate with the wireless terminal with least cost) is automatically determined by a data-processing system (i.e., server, etc.). This “closest” private branch exchange is referred to as the “visitor PBX.” 
     The data-processing system then updates, as necessary, the cost of routes between the wireless terminal and the private branch exchange with which the terminal is affiliated (i.e., the “home PBX”) and determines the least-cost route. In accordance with the first illustrative embodiment, the least-cost route information is disseminated to all enterprise private branch exchanges that have requested to subscribe to these updates, while in the second and third illustrative embodiments this information remains centralized at the data-processing system. Subsequently, calls made from the wireless terminal as well as calls directed to the wireless terminal via its home PPX are routed in accordance with the least-cost route information, thereby reducing the cost of calls in which the wireless terminal participates. 
     In accordance with the illustrative embodiments of the present invention, changes in the identity of an off-premises affiliated wireless terminal (e.g., a change of telephone number as a result of replacing the terminal&#39;s SIM card, etc.) are tracked and processed in a similar manner. In addition, the terminal&#39;s home PBX is accordingly notified of the identity change so that the PBX will forward the correct calls to the wireless terminal (i.e., calls made to the on-premises telephone number associated with the new wireless terminal identity). 
     The illustrative embodiments comprise: receiving at a data-processing system (i) an indication of the geo-location of a wireless telecommunications terminal, and (ii) an indication that the telephone number of said wireless telecommunications terminal has changed from M 1  to M 2 , wherein said wireless telecommunications terminal is associated with a telephone number N in the address space of a first private branch exchange, and wherein said telephone numbers M 1  and M 2  are not in the address space of said first private branch exchange; and transmitting from said data-processing system to said first private branch exchange a signal that causes said telephone number N to be mapped to said telephone number M 2  instead of M 1 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a schematic diagram of telecommunications system  100 , in accordance with the prior art. 
         FIG. 2  depicts an illustrative table mapping off-premises telephone numbers to on-premises telephone numbers, in accordance with the prior art. 
         FIG. 3  depicts a schematic diagram of telecommunications system  300 , in accordance with the illustrative embodiments of the present invention. 
         FIG. 4  depicts illustrative table  400  in accordance with the illustrative embodiments of the present invention. 
         FIG. 5  depicts the transmission of signals among elements of telecommunications system  300  during registration of affiliated wireless terminal  301  in response to an identity change at terminal  301 , in accordance with the first illustrative embodiment of the present invention. 
         FIG. 6  depicts the transmission of signals among elements of telecommunications system  300  during registration of affiliated wireless terminal  301  in response to a geo-locational change for terminal  301 , accordance with the first illustrative embodiment of the present invention. 
         FIG. 7  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  places a call, in accordance with the first illustrative embodiment of the present invention. 
         FIG. 8  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  receives a call that is directed to its associated on-premises terminal, in accordance with the first illustrative embodiment of the present invention. 
         FIG. 9  depicts the transmission of signals among elements of telecommunications system  300  during registration of affiliated wireless terminal  301  in response to an identity change at terminal  301 , in accordance with both the second and third illustrative embodiments of the present invention. 
         FIG. 10  depicts the transmission of signals among elements of telecommunications system  300  during registration of affiliated wireless terminal  301  in response to a geo-locational change for terminal  301 , in accordance with both the second and third illustrative embodiments of the present invention. 
         FIG. 11  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  places a call, in accordance with the second illustrative embodiment of the present invention. 
         FIG. 12  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  receives a call that is directed to its associated on-premises terminal, in accordance with the second illustrative embodiment of the present invention. 
         FIG. 13  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  places a call, in accordance with the third illustrative embodiment of the present invention. 
         FIG. 14  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  receives a call that is directed to its associated on-premises terminal, in accordance with the third illustrative embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 3  depicts a schematic diagram of telecommunications system  300 , in accordance with an illustrative embodiment of the present invention. Telecommunications system  300  comprises telecommunications network  105 , private branch exchanges  304 - 1  through  304 -P, where P is an integer greater than one, network  305 , off-premises affiliated wireless terminal  301 , telecommunications terminal  306 , and server  310 , interconnected as shown. 
     Private branch exchanges  304 - 1  through  304 -P are capable of providing all the functionality of private branch exchange  104  of the prior art, of transmitting and receiving signals among one another via network  305 , and of performing the functions described below and with respect to  FIGS. 5 through 14 . As will be appreciated by those skilled in the art, in some embodiments of the present invention private branch exchanges  304 - 1  through  304 -P might be instances of some other type of routing or switching element, rather than what is historically connoted by the terms “private branch exchange” or “PBX,” and it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention that comprise such alternative routing or switching elements. 
     Network  305  is capable of transporting signals among private branch exchanges  304 - 1  through  304 -P, of transmitting and receiving signals via telecommunications terminal  105 , and of transmitting signals to and receiving signals from server  310 , in well-known fashion. In some embodiments network  305  might be a public network (e.g., the PSTN, the Internet, etc.), while in some other embodiments network  305  might be a private network (e.g., leased lines, a virtual private network [VPN] over the Internet, etc.), while in still some other embodiments network  305  might be a combination of public and private networks. 
     Off-premises affiliated wireless terminal  301  is a wireless telecommunications terminal that is affiliated with some on-premises terminal of one of private branch exchanges  304 - 1  through  304 -P. The particular private branch exchange and on-premises terminal with which terminal  301  is affiliated is immaterial—it matters only that terminal  301  is affiliated with some on-premises terminal of the organization. 
     In accordance with the illustrative embodiment, affiliated wireless terminal  301  is capable of storing the Internet Protocol address of server  310 , and of transmitting signals to and receiving signals from server  310 . In addition, affiliated wireless terminal  301  is capable of accessing the contents of a table of information about the organization&#39;s private branch exchanges (e.g., their phone numbers, their geo-locations, etc.)—such as illustrative table  400  shown in  FIG. 4 —and of performing the functions described below and with respect to  FIGS. 5 through 14 . As will be appreciated by those skilled in the art, in some embodiments illustrative table  400  might be stored locally at affiliated wireless terminal  301 , while in some other embodiments illustrative table  400  might be stored elsewhere (e.g., server  310 , etc.) and accessed remotely by terminal  301 . In either case, it will be clear to those skilled in the art, after reading this disclosure, how to make and use affiliated wireless terminal  301 . 
     Server  310  is a data-processing system that is capable of transmitting and receiving signals via telecommunications network  105  and network  305 , of populating and updating illustrative table  400 , and of performing the functions described below and with respect to  FIGS. 5 through 14 . 
       FIG. 5  depicts the transmission of signals among elements of telecommunications system  300  during registration of affiliated wireless terminal  301  in response to an identity change at terminal  301 , in accordance with the first illustrative embodiment of the present invention. In particular,  FIG. 5  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. 
     As is the case for subsequent  FIGS. 6 through 14 ,  FIG. 5  is logical in nature; i.e., it depicts the transmission of signals among elements of telecommunications system  300  in an abstract, rather than physical, fashion, and does not include a depiction of any particular conduits of transmission (e.g., network  105 , network  305 , etc.) or intermediate nodes that might be present in the actual physical transmission path (e.g., a Session Initiation Protocol server for a Voice over Internet Protocol call, etc.). It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 5 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 5  can be performed simultaneously or in a different order than that depicted. 
     Signal transmissions are depicted in  FIG. 5  as arrows between nodes, where the temporal sequence of transmissions is in accordance with the arrows&#39; numerical labels, in ascending order. 
     At signal transmission  501 , one or more enterprise private branch exchanges  304  transmit a subscription request to server  310  requesting future updates on information including the identities of affiliated wireless terminals, the geo-locations of affiliated wireless terminals, and least-cost route information. (For convenience,  FIG. 5  shows two such signal subscription requests  501 , labeled  501 - 1  and  501 - 2 , submitted by home private branch exchange  304 -i and visitor private branch exchange  304 -j, respectively.) As will be appreciated by those skilled in the art, the transmission of subscription requests by a plurality of enterprise private branch exchanges might not necessarily occur simultaneously. 
     At signal transmission  502 , affiliated wireless terminal  301  transmits to server  310  an indication of its current geo-location (e.g. GPS coordinates, current cell ID, etc.), and an indication of a change in its identity (e.g., its user has inserted a new SIM card, etc.). 
     After receiving signal transmission  502 , server  310  determines which of the enterprise&#39;s private branch exchange is “closest” to the terminal (i.e., the identity of visitor private branch exchange  304 -j, which is already depicted in  FIG. 5 ) and updates least-cost routes, if necessary. 
     At signal transmission  503 , server  310  notifies wireless terminal  301  of the identity of visitor private branch exchange  304 -j for subsequent calls made from the terminal. 
     At signal transmission  504 , server  310  notifies home private branch exchange  304 -i of terminal  301 &#39;s new identity, and of any updated least-cost route information. In response to signal transmission  504 , home private branch exchange  304 -i accordingly updates its table mapping off-premises telephone numbers to on-premises telephone numbers. 
     At signal transmission  505 , server  310  notifies visitor private branch exchange  304 -j of the presence of wireless terminal  301  and any updated least-cost route information. 
       FIG. 6  depicts the transmission of signals among elements of telecommunications system  300  during registration of affiliated wireless terminal  301  in response to a geo-locational change for terminal  301 , accordance with the first illustrative embodiment of the present invention. In particular,  FIG. 6  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 6 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 6  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  601 , one or more enterprise private branch exchanges  304  transmit a subscription request to server  310  requesting future updates on information including the identities of affiliated wireless terminals, the geo-locations of affiliated wireless terminals, and least-cost route information. (For convenience,  FIG. 6  shows two such signal subscription requests  601 , labeled  601 - 1  and  601 - 2 , submitted by home private branch exchange  304 -i and visitor private branch exchange  304 -j, respectively.) As will be appreciated by those skilled in the art, the transmission of subscription requests by a plurality of enterprise private branch exchanges might not necessarily occur simultaneously. 
     At signal transmission  602 , affiliated wireless terminal  301  transmits to server  310  an indication of its current geo-location (e.g. GPS coordinates, current cell ID, etc.), in well-known fashion. 
     After receiving signal transmission  602 , server  310  determines the identity of visitor private branch exchange  304 -j (already depicted in  FIG. 6 ), and updates least-cost routes, if necessary. 
     At signal transmission  603 , server  310  notifies wireless terminal  301  of the identity of visitor private branch exchange  304 -j for subsequent calls made from the terminal. 
     At signal transmission  604 , server  310  notifies home private branch exchange  304 -i of terminal  301 &#39;s new identity, and of any updated least-cost route information. 
     At signal transmission  605 , server  310  notifies visitor private branch exchange  304 j of the presence of wireless terminal  301  and of any updated least-cost route information. 
       FIG. 7  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  places a call, in accordance with the first illustrative embodiment of the present invention. In particular,  FIG. 7  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 7 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 7  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  701 , affiliated wireless terminal  301  places a call by transmitting a signal to visitor private branch exchange  304 -j that specifies a particular destination (e.g., the telephone number of another wireless terminal, etc.) and instructs the PBX to route the call to the specified destination. 
     At signal transmission  702 , visitor private branch exchange  304 -j routes the call to home private branch exchange  304 -i, in well-known fashion. 
     At signal transmission  703 , home private branch exchange  304 -i extends the call to the destination, in well-known fashion. As will be appreciated by those skilled in the art, the call might be extended to a destination whose telephone number is in the address space of home private branch exchange  304 -i, or an extension within the address space of home private branch exchange  304 -i that does not correspond to any terminal, or might be routed externally to a terminal whose telephone number is outside the address space of home private branch exchange  304 -i (as depicted in  FIG. 7 ). 
       FIG. 8  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  receives a call that is directed to its associated on-premises terminal, in accordance with the first illustrative embodiment of the present invention. In particular,  FIG. 8  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 8 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 8  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  801 , home private branch exchange  304 -i receives a call that is directed to the on-premises telephone number associated with affiliated wireless terminal  301 . As will be appreciated by those skilled in the art, the call might originate from a terminal whose telephone number is in the address space of home private branch exchange  304 -i, or might originate from a terminal whose telephone number is outside the address space of home private branch exchange  304 -i (as depicted in  FIG. 8 ). 
     At signal transmission  802 , home private branch exchange  304 -i routes the call to visitor private branch exchange  304 -j, in well-known fashion. 
     At signal transmission  803 , visitor private branch exchange  304 -j extends the call to affiliated wireless terminal  301 , in well-known fashion. 
       FIG. 9  depicts the transmission of signals among elements of telecommunications system  300  during registration of affiliated wireless terminal  301  in response to an identity change at terminal  301 , in accordance with both the second and third illustrative embodiments of the present invention. In particular,  FIG. 9  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 9 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 9  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  901 , affiliated wireless terminal  301  transmits to server  310  an indication of its current geo-location (e.g. GPS coordinates, current cell ID, etc.), and an indication of a change in its identity (e.g., its user has inserted a new SIM card, etc.). 
     After receiving signal transmission  901 , server  310  determines which of the enterprise&#39;s private branch exchange is “closest” to the terminal (i.e., the identity of visitor private branch exchange  304 -j, which is already depicted in  FIG. 9 ) and updates least-cost routes, if necessary. 
     At signal transmission  902 , server  310  notifies wireless terminal  301  of the identity of visitor private branch exchange  304 -j for subsequent calls made from the terminal. 
     At signal transmission  903 , server  310  notifies home private branch exchange  304 -i of terminal  301 &#39;s new identity. In response to signal transmission  903 , home private branch exchange  304 -i accordingly updates its table mapping off-premises telephone numbers to on-premises telephone numbers. 
       FIG. 10  depicts the transmission of signals among elements of telecommunications system  300  during registration of affiliated wireless terminal  301  in response to a geo-locational change for terminal  301 , in accordance with both the second and third illustrative embodiments of the present invention. 
     In particular,  FIG. 10  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 10 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 10  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  1001 , affiliated wireless terminal  301  transmits to server  310  an indication of its current geo-location (e.g. GPS coordinates, current cell ID, etc.), in well-known fashion. 
     After receiving signal transmission  1001 , server  310  determines which of the enterprise&#39;s private branch exchange is “closest” to the terminal (i.e., the identity of visitor private branch exchange  304 -j, which is already depicted in  FIG. 10 ) and updates least-cost routes, if necessary. 
     At signal transmission  1002 , server  310  notifies wireless terminal  301  of the identity of visitor private branch exchange  304 -j for subsequent calls made from the terminal. 
     At signal transmission  1003 , server  310  notifies home private branch exchange  304 -i of terminal  301 &#39;s new identity. In response to signal transmission  1003 , home private branch exchange  304 -i accordingly updates its table mapping off-premises telephone numbers to on-premises telephone numbers. 
       FIG. 11  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  places a call, in accordance with the second illustrative embodiment of the present invention. In particular,  FIG. 11  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 11 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 11  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  1101 , affiliated wireless terminal  301  places a call by transmitting a signal to visitor private branch exchange  304 -j that specifies a particular destination (e.g., the telephone number of another wireless terminal, etc.) and instructs the PBX to route the call to the specified destination. 
     At signal transmission  1102 , visitor private branch exchange  304 -j routes the call to server  310 , in well-known fashion. 
     At signal transmission  1103 , server  310  routes the call to home private branch exchange  304 -i, in well-known fashion. 
     At signal transmission  1104 , the portion of the call connecting visitor private branch exchange  304 -j to home private branch exchange  304 -i is dropped from the call, and that portion is replaced by a new least-cost call that does not necessarily pass through server  310 . The remaining portion of the original call is then connected with the new call, in well-known fashion. 
     At signal transmission  1105 , the connected call is then extended to the specified destination, in well-known fashion. As will be appreciated by those skilled in the art, the call might be extended to a destination whose telephone number is in the address space of home private branch exchange  304 -i, or an extension within the address space of home private branch exchange  304 -i that does not correspond to any terminal, or might be routed externally to a terminal whose telephone number is outside the address space of home private branch exchange  304 -i (as depicted in  FIG. 11 ). 
       FIG. 12  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  receives a call that is directed to its associated on-premises terminal, in accordance with the second illustrative embodiment of the present invention. In particular,  FIG. 12  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 12 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 12  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  1201 , home private branch exchange  304 -i receives a call that is directed to the on-premises telephone number associated with affiliated wireless terminal  301 . As will be appreciated by those skilled in the art, the call might originate from a terminal whose telephone number is in the address space of home private branch exchange  304 -i, or might originate from a terminal whose telephone number is outside the address space of home private branch exchange  304 -i (as depicted in  FIG. 12 ). 
     At signal transmission  1202 , home private branch exchange  304 -i routes the call to server  310 , in well-known fashion. 
     At signal transmission  1203 , server  310  routes the call to visitor private branch exchange  304 -j, in well-known fashion. 
     At signal transmission  1204 , the portion of the call connecting home private branch exchange  304 -i to visitor private branch exchange  304 -j is dropped from the call, and that portion is replaced by a new least-cost call that does not necessarily pass through server  310 . The remaining portion of the original call is then connected with the new call, in well-known fashion. 
     At signal transmission  1205 , visitor private branch exchange  304 -j extends the call to affiliated wireless terminal  301 , in well-known fashion. 
       FIG. 13  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  places a call, in accordance with the third illustrative embodiment of the present invention. In particular,  FIG. 13  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 13 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 13  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  1301 , affiliated wireless terminal  301  places a call by transmitting a signal to visitor private branch exchange  304 -j that specifies a particular destination (e.g., the telephone number of another wireless terminal, etc.) and instructs the PBX to route the call to the specified destination. 
     At signal transmission  1302 , visitor private branch exchange  304 -j routes the call to server  310 , in well-known fashion. 
     At signal transmission  1303 , server  310  routes the call to home private branch exchange  304 -i along a route that includes visitor private branch exchange  304 -j, in well-known fashion. 
     At signal transmission  1304 , the portion of the call connecting visitor private branch exchange  304 -j to server  310  back to visitor private branch exchange  304 -j is dropped from the call. 
     At signal transmission  1305 , the call is then extended to the specified destination, in well-known fashion. As will be appreciated by those skilled in the art, the call might be extended to a destination whose telephone number is in the address space of home private branch exchange  304 -i, or an extension within the address space of home private branch exchange  304 -i that does not correspond to any terminal, or might be routed externally to a terminal whose telephone number is outside the address space of home private branch exchange  304 -i (as depicted in  FIG. 13 ). 
     In some other embodiments of the present invention, signal transmission signal transmission  1304  might be omitted, and at signal transmission  1303  server  310  might instead establish a new call to home private branch exchange  304 -i along a route that includes visitor private branch exchange  304 -j. In such embodiments, the portions of the original and new calls connecting visitor private branch exchange  304 -j and server  310  are subsequently dropped, and the remaining portions of the original and new calls are then connected, in well-known fashion. 
     In still some other embodiments, at signal transmission  1303  server  310  might transmit a signal that instructs visitor private branch exchange  304 -j to route the call to home private branch exchange  304 -i, in which case at signal transmission  1304  visitor private branch exchange  304 -j carries out this instruction. 
       FIG. 14  depicts the transmission of signals among elements of telecommunications system  300  when affiliated wireless terminal  301  receives a call that is directed to its associated on-premises terminal, in accordance with the third illustrative embodiment of the present invention. In particular,  FIG. 14  depicts the transmission of signals among affiliated wireless terminal  301 , server  310 , home private branch exchange  304 -i, and visitor private branch exchange  304 -j. It will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in accordance with  FIG. 14 ; moreover, it will be clear to those skilled in the art, after reading this disclosure, which signal transmissions of  FIG. 14  can be performed simultaneously or in a different order than that depicted. 
     At signal transmission  1401 , home private branch exchange  304 -i receives a call that is directed to the on-premises telephone number associated with affiliated wireless terminal  301 . As will be appreciated by those skilled in the art, the call might originate from a terminal whose telephone number is in the address space of home private branch exchange  304 -i, or might originate from a terminal whose telephone number is outside the address space of home private branch exchange  304 -i (as depicted in  FIG. 14 ). 
     At signal transmission  1402 , home private branch exchange  304 -i routes the call to server  310 , in well-known fashion. 
     At signal transmission  1403 , server  310  routes the call to home private branch exchange  304 -i along a route that includes visitor private branch exchange  304 -j, in well-known fashion. 
     At signal transmission  1404 , the portion of the call connecting home private branch exchange  304 -i to server  310  back to home private branch exchange  304 -i is dropped from the call. 
     At signal transmission  1405 , visitor private branch exchange  304 -j extends the call to affiliated wireless terminal  301 , in well-known fashion. 
     In some other embodiments of the present invention, signal transmission signal transmission  1404  might be omitted, and at signal transmission  1403  server  310  might instead establish a new call to visitor private branch exchange  304 -j along a route that includes home private branch exchange  304 -i. In such embodiments, the portions of the original and new calls connecting home private branch exchange  304 -i and server  310  are subsequently dropped, and the remaining portions of the original and new calls are then connected, in well-known fashion. 
     In still some other embodiments, at signal transmission  1403  server  310  might transmit a signal that instructs home private branch exchange  304 -i to route the call to visitor private branch exchange  304 -j, in which case at signal transmission  1404  home private branch exchange  304 -i carries out this instruction. 
     As will be appreciated by those skilled in the art, although the illustrative embodiment is disclosed in the context of reducing toll charges, it will be clear to those skilled in the art, after reading this disclosure, how to make and use other embodiments of the present invention that reduce other kinds of costs (e.g., transmission delay, distance traveled, number of network segments traversed, etc.). 
     As will be further appreciated by those skilled in the art, although the illustrative embodiment does not explicitly include any mechanism by which private branch exchanges  304  authenticate affiliated terminal  301 , such authentication methods are well-known in the art, and it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention that incorporate such methods. 
     It is to be understood that the disclosure teaches just one example of the illustrative embodiment and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.