Abstract:
A method and apparatus are disclosed for routing calls over an organization&#39;s private network of private branch exchanges. In particular, when a member of the organization (e.g., an employee, etc.) places a call from his or her affiliated off-premises telecommunications terminal (e.g., cell phone, etc.), the call is automatically routed to its destination through at least a portion of the private network of private branch exchanges when doing so reduces the cost of the call. In the illustrative embodiment, the call routing is performed automatically and transparently via software on the affiliated terminals (i.e., employees&#39; cell phones) and on the organization&#39;s private branch exchanges.

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to telecommunications in general, and, more particularly, to emulating the behavior of a private branch exchange at a second private branch exchange. 
       BACKGROUND OF THE INVENTION  
       [0002]    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. 
         [0003]      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. 
         [0004]    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. 
         [0005]    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 . 
         [0006]    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.    
         [0007]      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 . 
         [0008]    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 . 
         [0009]    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. 
         [0010]    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 . 
       SUMMARY OF THE INVENTION  
       [0011]    The present invention is applicable to organizations that have private branch exchanges (PBXs) at two or more different sites, and a private network (e.g., leased lines, a virtual private network [VPN] over the Internet, etc.) that connects some or all of the private branch exchanges. In particular, the present invention pertains to any call from an affiliated off-premises terminal (typically, an employee&#39;s cell phone) to any destination (e.g., another cell phone, a wireline terminal, a private branch exchange, etc.). For example:
       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.       
 
         [0015]    In accordance with the illustrative embodiment, when an employee places a call from his or her affiliated off-premises terminal (e.g., cell phone, etc.), the call is automatically routed to its destination through the organization&#39;s private network of private branch exchanges when doing so reduces the cost of the call. For example, suppose an employee in Finland and places a call from his cell phone to a customer in Spain. The call might be routed from his cell phone to the customer&#39;s terminal through the organization&#39;s private branch exchanges in Helsinki, Munich, Paris, and Madrid, thereby minimizing the toll charges for the call by maximizing the portion of the route over the organization&#39;s private network. (Note that in accordance with the illustrative embodiment, it is immaterial whether the employee works at the organization&#39;s Helsinki branch, or is an employee of the organization&#39;s New York branch and is on travel in Finland.) In the illustrative embodiment, the call routing is performed automatically and transparently via software on the affiliated terminals (i.e., employees&#39; cell phones) and on the organization&#39;s private branch exchanges. 
         [0016]    The illustrative embodiment comprises: receiving at a telecommunications terminal an input for placing a first call to a destination D; and placing a second call, in response to the input, from the telecommunications terminal to a first of a plurality of associated private branch exchanges; wherein a call from the telecommunications terminal to the first private branch exchange incurs no more cost than a call from the telecommunications terminal to any other of the plurality of associated private branch exchanges. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0017]      FIG. 1  depicts a schematic diagram of telecommunications system  100 , in accordance with the prior art. 
           [0018]      FIG. 2  depicts an illustrative table that maps off-premises telephone numbers to on-premises telephone numbers, in accordance with the prior art. 
           [0019]      FIG. 3  depicts a schematic diagram of telecommunications system  300 , in accordance with the illustrative embodiment of the present invention. 
           [0020]      FIG. 4  depicts illustrative table  400  that is stored at affiliated telecommunications terminal  301 , in accordance with the illustrative embodiment of the present invention. 
           [0021]      FIG. 5  depicts a flowchart of the salient tasks of affiliated telecommunications terminal  301  and private branch exchanges  304 , as shown in  FIG. 3 , in accordance with the illustrative embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0022]      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, private network  305 , off-premises affiliated telecommunications terminal  301 , and telecommunications terminal  306 , interconnected as shown. 
         [0023]    Private branch exchanges  304 - 1  through  304 -P provide all the functionality of private branch exchange  104  of the prior art, and are also capable of performing the tasks described below and with respect to  FIG. 5 . 
         [0024]    Off-premises affiliated telecommunications terminal  301  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, wireless telecommunications terminal  301  is capable of storing 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 tasks described below and with respect to  FIG. 5 . 
         [0025]      FIG. 5  depicts a flowchart of the salient tasks of affiliated telecommunications terminal  301  and of private branch exchanges  304 - 1  through  304 -P, in accordance with the illustrative embodiment of the present invention. It will be clear to those skilled in the art which tasks depicted in  FIG. 5  can be performed simultaneously or in a different order than that depicted. 
         [0026]    At task  501 , affiliated terminal  301  receives an input from its user for placing a call to telecommunications terminal  306 , in well-known fashion. 
         [0027]    At task  502 , affiliated terminal  301  first determines whether a call from affiliated terminal  301  to terminal  306  would incur less cost if a portion of the route travels over private network  305 . As will be appreciated by those skilled in the art, this determination might be based on a variety of factors such as the particular billing plan for affiliated terminal  301 , the current time and date, the network that affiliated terminal is currently connected to (e.g., Verizon Wireless USA, etc.), the entry point at which affiliated terminal  301  connects to this network (e.g., the base station currently serving affiliated terminal  301 , etc.), the current geo-location of affiliated terminal  301  (if known), and so forth. As will further be appreciated by those skilled in the art, in some embodiments affiliated terminal  301  might make this determination itself (e.g., based on information stored locally in table  400 , etc.), while in some other embodiments affiliated terminal  301  might send a query to another entity (e.g., a base station, a server, a geo-location system, etc.) to make this determination and return the result to affiliated terminal  301 . As will further be appreciated by those skilled in the art, in some other embodiments of the present invention the cost of a call might be quantified by some non-monetary metric rather than toll charges, and it will be clear to those skilled in the art, after reading this disclosure, how to make and use such embodiments. 
         [0028]    If it is determined that a call through private network  305  would incur less cost, then affiliated terminal  301  selects which private branch exchange  304 - k,  where k is a positive integer less than or equal to P, to call in order to minimize cost. For example, suppose the user of affiliated terminal  301  is in New York&#39;s Grand Central Station and inputs a command to the terminal to call a customer. Then affiliated terminal  301  might select the private branch exchange of the organization&#39;s Manhattan office as the “best” PBX to call, because it minimizes the portion of the route that is not over private network  305 , and therefore (presumably) minimizes the cost of the call. As in the determination above, the cost of a particular route might be based on a variety of factors such as the billing plan, the current time and date, etc., and thus the selection of the best private branch exchange to call will depend on these factors. Furthermore, as in the determination above, in some embodiments affiliated terminal  301  might select the best private branch exchange itself (e.g., based on information stored locally in table  400 , etc.), while in some other embodiments affiliated terminal  301  might send a query to another entity to select the private branch exchange and return the result to affiliated terminal  301 . 
         [0029]    At task  503 , a branch is executed based on the first determination of task  502 —i.e., whether a call from affiliated terminal  301  to terminal  306  would incur less cost if a portion of the route travels over private network  305 . If this determination is affirmative, the method of  FIG. 5  proceeds to task  504 , otherwise execution continues at task  507 . 
         [0030]    At task  504 , affiliated terminal  301  places a call to selected private branch exchange  304 - k,  and transmits telecommunications terminal  306 &#39;s phone number to PBX  304 - k  as the ultimate destination of the call. In accordance with the illustrative embodiment, affiliated terminal  301  calls a special extension of private branch exchange  304 - k  that is not associated with any telecommunications terminal, but rather is reserved for the routing of incoming calls to an arbitrary destination (e.g., an unaffiliated off-premises terminal, an affiliated off-premises terminal, an on-premises terminal, another private branch exchange, etc.). As will be appreciated by those skilled in the art, some other embodiments of the present invention might utilize an alternative mechanism for instructing PBX  304 - k  to route the call to telecommunications terminal  306 . 
         [0031]    At task  505 , private branch exchange  304 - k  determines the least-cost route R from itself to terminal  306 , in well-known fashion (route R might or might not include additional private branch exchanges  304 ). 
         [0032]    At task  506 , private branch exchange  304 - k  routes the call to terminal  306  via the least-cost route R determined at task  505 , in well-known fashion. After task  506  is completed, the method of  FIG. 5  terminates. 
         [0033]    At task  507 , affiliated terminal  301  places a call to terminal  306  over telecommunications network  105  in normal fashion. After task  507  is completed, the method of  FIG. 5  terminates. 
         [0034]    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.). 
         [0035]    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. 
         [0036]    It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc. 
         [0037]    Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.