Telecommunications – Radiotelephone system – Message storage or retrieval
Reexamination Certificate
1998-12-28
2001-08-28
Maung, Nay (Department: 2744)
Telecommunications
Radiotelephone system
Message storage or retrieval
C455S412100, C455S433000, C455S561000
Reexamination Certificate
active
06282416
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to mobile-to-mobile telecommunications and in particular to delivering calls from an originating mobile switching center (MSC-O) to a called mobile's voice mailbox. Still more particularly, the present invention relates to employing existing message definitions to obtain a temporary local directory number (TLDN) to facilitate call delivery from the MSC-O to the called mobile's voice mailbox.
2. Description of the Related Art
Mobile service subscribers may currently obtain both “roaming” access, or wireless service outside a home service area, in addition to many other services including incoming call redirection to voice mail. When a call attempts to terminate to a mobile, the home mobile switching center (MSC-H) handles the call and, if necessary, redirects the call to the serving mobile switching center (MSC-S) in a process known as call delivery. In the event that the called mobile cannot or does not accept the incoming call, the MSC-S may request, via signaling messages that the MSC-H redirect the incoming call to the called mobile's voice mailbox. Generally, the MSC-H will have a direct connect trunks to the voice mail system, thereby allowing a non-PSTN routable numbers to be used as the redirection number to steer the redirected call to the called mobile's voice mailbox. For example, the redirection number used for voice mail could be ‘#4258675555’. Since the use of such non-PSTN routable numbers requires special digit translations understood only by the MSC-H, all calls to a mobile must first route to the mobile's MSC-H before call delivery occurs to the MSC-S. This ensures that the MSC-H can redirect the call to the called mobile's voice mailbox if necessary.
For reasons described in the paragraph above, mobile-to-mobile calls must also first route the called mobile's MSC-H. The originating mobile switching center (MSC-O) serving the originating mobile cannot redirect the call to the called mobile's voice mailbox based on a non-PSTN routable number. When the mobile switching center serving the called mobile (MSC-S) determines that call redirection to voice mail is required, a request to invoke redirection to voice mail is signaled to the MSC-H. In the ANSI-41 wireless networking standard, this message is the Redirection Request (REDREQ) message; other wireless networking standards such as the Mobile Application Part signaling used for GSM networks implement a similar mechanism to redirect incoming calls to voice mail.
The mechanism described above incurs substantial use of trunk resources. A call must be connected from the MSC-O serving the originating mobile to the called mobile's MSC-H and thence to the MSC-S serving the called mobile. A mobile in Seattle, Wash. calling Dallas-based mobile that happens roaming in Portland, Ore. involves a trunk from the Seattle MSC-O to the Dallas MSC-H and thence to the Portland MSC-S rather than routing directly from Seattle to Portland. The indirect routing through Dallas is required in order to ensure that the call can be redirected by the Dallas MSC-H to voice mail if requested by the Portland MSC-S. In addition to wasteful use of trunk resources, this type of call routing increases voice transmission delay which may be detrimental to perceived audio quality. Some MSC's implement digital mobile voice coder bypass techniques in which digitally encoded speech may be passed directly from mobile to mobile provided that the bit patterns not be altered by transmission equipment. Since long-haul trunks require echo cancellation equipment, such voice coder bypass techniques will not operate on long-haul trunk circuits, causing voice quality degradation because the MSC-O must decode the digitally compressed voice signal and then the MSC-S must re-encode and digitally recompress the voice signal.
SUMMARY OF THE INVENTION
It is therefore one object of the present invention to provide an improved method and apparatus for mobile-to-mobile telecommunications.
It is another object of the present invention to provide an improved method and apparatus for delivering calls from an MSC-O to a called mobile's voice mailbox.
It is yet another object of the present invention to provide a method and apparatus for employing existing message definitions to utilize a TLDN to facilitate call delivery from the MSC-O serving the calling mobile to the called mobile's voice mailbox.
The foregoing objects are achieved as is now described. Upon determining that call redirection to a voice mailbox is required (based on receipt of redirection request message from the MSC-S serving the called mobile), the MSC-O transmits a transfer-to-number request (TRANUMREQ) signal to the called mobile's home location register (HLR). The HLR then transmits a routing request (ROUTREQ) signal to an adjunct mobile switching center (MSC-A) which supports direct trunk connections to the voice mail system that hosts the called mobile's voice mailbox. The ROUTREQ message not only serves as an indication to the MSC-A that a TLDN is being requested, but it also provides the MSC-A with the mailbox number to which a call terminating to the TLDN is to be connected. The MSC-A allocates a TLDN for the call that will be redirected to voice mail and associates the mailbox number with this TLDN. The assigned TLDN is returned via signaling messages to the HLR via the routing request return result (routreq) which in turn relays the TLDN to the MSC-O via the transfer-to-number request return result (tranumreq). The MSC-O then redirects the call via either public or private voice transmission facilities to the MSC-A, the MSC-A uses the mailbox number provided by the HLR to connect to the called mobile's voice mailbox.
The capability of connecting to a called mobile's voice mailbox via a PSTN-routable TDLN number eliminates the requirement of routing mobile-to-mobile calls through the called mobile's MSC-H. Instead, mobile-to-mobile calls can be routed directly from the MSC-O to the MSC-S and, if call redirection to the called mobile's voice mailbox is required, the MSC-O is capable of connecting to the called mobile's voice mailbox via the PSTN. In addition to dramatically reducing transmission back-haul requirements (and thereby improving voice quality and reducing transmission costs), this invention allow the called mobile's carrier to centralize the special translations required to connect to voice mail systems at the MSC-A. Previously, the special translations required to handle voice mail redirection were distributed if the home carrier's network consisted of multiple MSC-H switches.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.
REFERENCES:
patent: 5506888 (1996-04-01), Hayes et al.
patent: 5627877 (1997-05-01), Penttonen
patent: 5901359 (1999-05-01), Malmstrom
patent: 6011969 (2000-01-01), Vargas et al.
patent: 6055423 (2000-04-01), Calabrese et al.
Bracewell & Patterson L.L.P.
Crane John D.
Maung Nay
Nortel Networks Limited
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