Abstract:
An access network adapted to be coupled to a local exchange over a high-speed link is provided. The access network has a digital line carrier having a port adapted to be coupled to the high-speed link and a plurality of line cards. Each line card has at least one port adapted to be coupled to a transceiver. The digital line carrier selectively connects a transceiver associated with a port of one of the plurality of line cards of the digital line carrier with a transceiver associated with a port of another line card of the digital line carrier based on a signal sent to and returned by the local exchange.

Description:
TECHNICAL FIELD 
   The present invention relates generally to the field of telecommunications and, in particular, to an intracall feature for an access network. 
   BACKGROUND 
   Many telecommunication systems have a number of access networks coupled to a local exchange. Each access network usually includes a digital line carrier coupled to the local exchange by a plurality of high-speed digital lines, e.g., a T1 or an E1 line. Typically, an interface, such as a V5.2 interface, defines the switching and signaling protocol between the digital line carrier and the local exchange. The access network provides for the connection of a number of transceivers, e.g., telephones, to the public switched telephone network (PTSN). 
   Typically, when using one of these systems to place a telephone call, for example, between a first transceiver and a second transceiver, the first transceiver is taken off hook, and the number of the second transceiver is entered into the first transceiver. The number is transmitted to the local exchange via a digital line carrier of an access network. Subsequently, the local exchange initiates a call establishment process, e.g., a V5.2 call establishment process, to complete the call to the second transceiver. In a typical case, each transceiver is associated with a different digital line carrier and access network. Further, the call establishment process includes allocating a time slot to each of the first and second transceivers in the high-speed digital links between the digital line carrier and the local exchange. However, in some cases, both transceivers are associated with the same digital line carrier. 
   One problem with the above setup is that when the first and second transceivers belong to the same access network and are coupled to the same digital line carrier, the first and second transceivers connect through the local exchange. This increases the load on the digital high-speed lines between the digital line carrier and the local exchange and thus increases the required number of lines. 
   For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for access networks that more effectively use available bandwidth in high-speed digital links between the local exchange and the digital line carrier. 
   SUMMARY 
   The above-mentioned problems with access networks and digital line carriers and other problems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. Embodiments of the present invention free up bandwidth between a digital line carrier and the local exchange by allowing calls between transceivers of the same digital line carrier (hereinafter “Intracall”) to connect through the digital line carrier. 
   More particularly, in one embodiment, an access network adapted to be coupled to a local exchange over a high-speed link is provided. The access network has a digital line carrier having a port adapted to be coupled to the high-speed link and a plurality of line cards. Each line card has at least one port adapted to be coupled to a transceiver. The digital line carrier selectively connects a transceiver associated with a port of one of the plurality of line cards of the digital line carrier with a transceiver associated with a port of another line card of the digital line carrier based on a signal sent to and returned by the local exchange. 
   In another embodiment, a method for connecting two transceivers coupled to a digital line carrier of an access network coupled to a local exchange is provided. The method involves connecting the two transceivers at the local exchange. Upon connecting the two transceivers at the local exchange a tone is transmitted from the digital line carrier to the local exchange. A tone is then received from the local exchange at the digital line carrier in response to the tone from the digital line carrier. Based on receiving the tone at the digital line carrier, the two transceivers are disconnected at the local exchange and are connected at the digital line carrier. 
   Other embodiments are described and claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of an embodiment of an access network according to the teachings of the present invention. 
       FIG. 2  is a flow diagram of an embodiment of a method for connecting two transceivers at a digital line carrier according to the teachings of the present invention. 
       FIG. 3  is a flow diagram of an embodiment of a method for disconnecting two transceivers at a digital line carrier according to the teachings of the present invention. 
   

   DETAILED DESCRIPTION 
   In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. 
   Embodiments provide for connecting two transceivers belonging to the same access network and coupled to the same digital line carrier at the digital line carrier rather than at a local exchange that is coupled to the access network. This reduces the load on the local exchange and reduces the number of lines between the digital line carrier and the local exchange. 
   One embodiment of the present invention is shown as access network  100  in FIG.  1 . Access network  100  includes digital line carrier  102  that is adapted to be coupled to a local exchange  110  over a high-speed link  112 . In one embodiment, high-speed link  112  comprises one or more high-speed digital lines, e.g., T1/E1 lines. Access network  100  includes a central unit  114 . Central unit  114 , in one embodiment, is co-located at the local exchange. In other embodiments, central unit  114  is located separate from the local exchange. Central unit  114  has a port  114   a  adapted to be coupled to the local exchange and a port  114   b  that is coupled to high-speed link  112 . Digital line carrier  102  has a network interface card  102   a . Network interface card  102   a  has a port  108  adapted to be coupled to high-speed link  112 . 
   Digital line carrier  102  has line cards  102   b   1 - 102   b   N , e.g., ISDN cards, POTS cards, or the like. Line cards  102   b   1 - 102   b   N  respectively have ports  102   b   11 - 102   b   NN . Each of ports  102   b   11 - 102   b   NN  is adapted to be coupled to a transceiver. For example, transceivers  104  and  106  are respectively coupled to ports  102   b   11  and  102   b   22  by lines  104   a  and  106   a , as shown in FIG.  1 . In one embodiment, one or more of line cards  102   b   1 - 102   b   N  have multiple ports and transceivers, e.g., transceivers  104  and  106 , are respectively coupled to one of the multiple ports of one of the line cards. In one embodiment, transceivers  104  and  106  are telephones. In another embodiment, switching and signaling between digital line carrier  102  and local exchange  110  is accomplished using a V5.2 protocol. 
   Method  200 , illustrated in the flow diagram of  FIG. 2 , is one embodiment of a method of the present invention for connecting transceivers  104  and  106  at digital line carrier  102 . Method  200  includes taking one of transceivers  104  and  106  off hook, e.g., transceiver  104  as depicted by arrow  202 . Taking transceiver  104  off hook includes sending connection initiation information from transceiver  104  to local exchange  110 , e.g., entering the number of the other of transceivers  104  and  106 , e.g., transceiver  106 . 
   Then, a connection establishment process is initiated between local exchange  110  and digital line carrier  102 , as depicted by arrow  204 . In one embodiment, the connection establishment process involves allocating time slots in high-speed link  112  to each of transceivers  104  and  106  at local exchange  110 . In another embodiment, the connection establishment process includes using a V5.2 protocol. Upon completion of the connection establishment process, transceiver  106  responds, for example, by ringing. Then, transceiver  106  is taken off hook, e.g., answering the telephone, which connects transceiver  106  to local exchange  110 , as depicted by arrow  206 . This connects transceivers  104  and  106  at local exchange  110 , as shown by arrow  210 . In other embodiments, local exchange  110  starts a billing process, as indicated by arrow  211 , after transceiver  106  is connected to local exchange  110 . 
   Upon connecting transceivers  104  and  106  at local exchange  110 , digital line carrier  102  transmits a tone to local exchange  110 , as indicated by arrow  212 . Local exchange  110  subsequently transmits a tone back to digital line carrier  102 , as indicated by arrow  214 . Upon receiving the tone from local exchange  110 , digital line carrier  102  determines that this is an “Intracall,” e.g., a call between two transceivers of the same digital line carrier. To save bandwidth in high-speed link  112 , digital line carrier  102  connects transceivers  104  and  106  at digital line carrier  102 , as shown by arrow  216 . In embodiments where time slots are allocated to each of transceivers  104  and  106  at local exchange  110 , connecting transceivers  104  and  106  at digital line carrier  102  releases each of the allocated time slots, so these time slots can be used for other connections. 
   Upon connecting transceivers  104  and  106  at digital line carrier  102 , digital line carrier  102  transmits a block signal to local exchange  110 , as indicated by arrow  218 . The block signal tells local exchange  110  to block incoming transmissions that are destined for transceivers  104  and  106 . When local exchange  110  receives the block signal, local exchange  110  disconnects transceivers  104  and  106  at the local exchange and blocks incoming transmissions that are destined for transceivers  104  and  106 . Local exchange  110  subsequently transmits a block acknowledgement message to digital line carrier  102  acknowledging that incoming transmissions destined for transceivers  104  and  106  are blocked, as indicated by arrow  220 . In embodiments including the billing process depicted by arrow  211 , local exchange  110  terminates the billing process, as indicated by arrow  222 , after digital line carrier  102  receives the block acknowledgement message. 
     FIG. 3  is a flow diagram illustrating one embodiment of a method of the present invention for disconnecting transceivers  104  and  106  at digital line carrier  102 . The method includes placing transceiver  104  on hook, e.g., hanging up the telephone, as depicted by arrow  302 . This disconnects transceiver  104  from digital line carrier  102 . Subsequently, digital line carrier  102  transmits an unblock signal to local exchange  110  that tells local exchange  110  to unblock incoming transmissions that are destined for transceiver  104 , as indicated by arrow  304 . Transceiver  106  is placed on hook, e.g., hanging up the telephone, as depicted by arrow  306 . This disconnects transceiver  106  from digital line carrier  102 . Subsequently, digital line carrier  102  transmits an unblock signal to local exchange  110  that tells local exchange  110  to unblock incoming transmissions that are destined for transceiver  106 , as indicated by arrow  308 . 
   CONCLUSION 
   Embodiments of the present invention have been described. The embodiments provide an access network and a method for connecting two transceivers coupled to a digital line carrier of an access network coupled to a local exchange. These embodiments provide for connecting two transceivers belonging to the same access network and coupled to the same digital line carrier at the digital line carrier rather than at the local exchange, reducing the load on the local exchange and the number of lines between the digital line carrier and the local exchange. 
   Although specific embodiments have been illustrated and described in this specification, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. For example, transceivers  104  and  106  can be interchanged in  FIGS. 2 and 3  and in the corresponding discussion above. Moreover,  FIGS. 2 and 3  show that the transceiver that is taken off hook first, e.g., transceiver  104  in  FIG. 2 , is placed on hook first, e.g., transceiver  104  in FIG.  3 . However, the transceiver that is taken off hook first is not limited to being placed on hook first. Rather, the respective transceivers can be placed on hook in any order.