Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2001-09-18
2004-10-12
Ramakrishnaiah, Melur (Department: 2643)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S437000, C455S439000
Reexamination Certificate
active
06804518
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of communication systems, and more particularly, to a method of routing a voice call to a mobile station that is engaged in a packet data call.
BACKGROUND OF THE INVENTION
The Code Division Multiple Access (CDMA) IS-2000 network supports concurrent services functionality (packet data and voice). In particular, a mobile station (MS) operating in the IS-2000 network may be in a state where it is engaged in a packet data call and simultaneously available for voice originations and terminations. If the MS has undergone an intersystem hard handoff (HHO) prior to entering this state or an intersystem HHO occurs while the MS is in this state, the MS will not register with its serving mobile switching center (MSC) as long as the data call remains active. When this occurs, delivery of mobile terminated voice calls to the MS is complex and may lead to excessive intersystem messaging. For example, an anchor MSC could send ANSI-41 intersystem setup messages to a list of MSCs that might be serving the MS to setup the call. Those not serving the MS would reply with a setup result of “unsuccessful”. However, it is unclear how the MSC would determine the members of the list.
FIG. 1
illustrates the problem of the delivery of mobile terminated voice calls after an intersystem HHO has occurred.
As shown in
FIG. 1
, the MS
118
is engaged in a packet data call with the PDSN
120
. While the MS
118
is engaged in the data call, the originating MSC
102
receives a voice call attempt. The originating MSC
102
obtains the location of the MS
118
from the Home Location Register (HLR)
104
in the MS's home network. The HLR
104
obtains the circuit address, specifically the temporary local directory number, of the MS
118
from the anchor MSC
106
and a circuit bearer path (physical circuit that carries the bearer data) for the voice call is established to the anchor MSC
106
. The anchor MSC
106
is the first MSC that the MS
118
registers with. The MS
118
receives access network management and control from the anchor MSC
106
via the Base Site Controller (BSC)
108
and Base Transceiver Station (BTS)
109
. When the MS
118
undergoes an intersystem HHO, a different MSC shown as a first serving MSC
110
will begin “serving” the MS
118
. The MS
118
will now receive access network management and control from the first serving MSC
110
via the BSC
112
and BTS
113
. However, the MS
118
will not register with the first serving MSC
110
as long as the data call remains active. As designated by the dotted lines in
FIG. 1
, the anchor MSC
106
may not have the Signaling System 7 (SS7) address of the first serving MSC
110
and may not have a bearer path to deliver a voice call to the first Serving MSC
110
. (The SS7 address is what the MSC uses to address signaling messages to other network elements.) Thus, the MS
118
will be unable to communicate with the first serving MSC
110
via the BSC
112
and BTS
113
for receipt of the voice call. The problem continues if yet another HHO occurs to a second serving MSC
114
. Again, the anchor MSC
106
may not have the SS7 address of the second serving MSC
114
and may not have a bearer path to deliver a voice call to the second Serving MSC
114
via the BSC
116
and BTS
117
. Currently, Chapter 5, Section 6 of Cellular Radiotelecommunications Intersystem Operations (ANSI/TIA/EIA-41-D), hereinafter referred to as ANSI-41, defines messaging that can overcome this problem for most mobile terminated voice call delivery scenarios. However, the messaging is complex and may not be available on all MSCs. A copy of ANSI-41 may be obtained via a world wide web site located at www.tiaonline.org, or by writing to Telecommunications Industry Association, 1300 Pennsylvania Ave., Suite 350, Washington, D.C. 20004 USA.
Thus, there is a need for a method of forcing a MS to re-register its location after an intersystem HHO without significantly impacting ongoing data sessions to eliminate the need for current complex processing. Such a method would allow routing of a voice call to the MS while the MS is engaged in a packet data session.
REFERENCES:
patent: 2002/0082018 (2002-06-01), Coskun et al.
patent: 2003/0232629 (2003-12-01), Jang et al.
Core Ronald Scott
Johnson Lloyd J.
Peterson James P.
Turner Steven K.
Motorola Inc.
Pace Lalita W.
Ramakrishnaiah Melur
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