Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-12-15
2003-02-11
Cumming, William (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
Reexamination Certificate
active
06519454
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a wireless communications system providing call transfer for an incoming call to a mobile subscriber unit.
BACKGROUND OF THE INVENTION
Wireless communications systems attempt to provide telephone services to mobile subscribers that are equivalent to traditional landline telephone networks. This objective is complicated by the fact that mobile subscribers may roam away from their home market. Different wireless markets may utilize different manufacturer's equipment. Consequently, mobile subscribers may not be able to use wireless features offered in their home markets if the serving markets do not support the features.
As an example, “call transfer” is a common landline telephone service in which a subscriber can transfer an incoming call to another designated telephone party. However, this service is not always available in a wireless communications system. Not all mobile switching centers (MSC), which provides the switching functionality of a wireless communications system, support call transfer. If an incoming call is delivered to the mobile subscriber's home market that supports call transfer and the mobile subscriber has roamed to another (serving) market, call transfer may not be available to the mobile subscriber. Moreover, even if call transfer is supported by the plurality of MSC's which an incoming call spans, the prior art requires that inter-MSC telephone facilities be configured between the MSC's. Having to support these facilities increases the cost to the wireless service provider, thus increasing the price of service to the wireless subscriber. Thus, there is an important need to provide ubiquitous call transfer to the wireless subscriber.
FIG. 1
illustrates an architecture supported by a wireless communications system that supports an incoming call to a mobile subscriber unit associated with a wireless subscriber in accordance with prior art. In
FIG. 1
, an incoming call originates from public switching telephone network (PSTN)
100
for mobile subscriber unit
105
. The incoming call is delivered to originating mobile switching center (“originating” MSC)
101
(in which mobile subscriber unit
105
may or may not be located) through telephone facility
106
. Typically, mobile subscriber unit
105
is provisioned (homed) at originating MSC
101
, and PSTN
100
delivers all incoming calls to originating MSC
101
.
If mobile subscriber unit
105
is not located within a region served by originating MSC
101
, the incoming call must be delivered to serving mobile switching center (serving MSC)
103
in which mobile subscriber unit
105
is located. Originating MSC
101
determines where mobile subscriber unit is located by querying home location register (HLR)
102
using data facility
107
. Whenever mobile subscriber unit
105
changes locations so that it is located in a region of a different serving MSC, HLR
102
is updated with the updated location through data facility
109
. HLR
102
may be physically separate entity or may be physically located at originated MSC
101
. The incoming call is delivered to serving MSC
103
through inter-mobile switching center (inter-MSC) facility
108
. Serving MSC
103
connects the incoming call through base station
104
(where mobile subscriber unit is currently located) over trunk
110
. Base station
104
establishes radio connection
111
to mobile subscriber unit
105
, thus completing the incoming call between PSTN
100
and mobile subscriber unit
105
. The telephone path of the incoming call consists of telephone facility
106
, inter-MSC facility
108
, trunk
110
, and radio connection
111
. Since the telephone path is completed at serving MSC
103
, if serving MSC
103
is situated in a billing zone that is associated with long-distance rates, the party initiating the incoming call may be charged at a long-distance rate even though the designated party to which the call was transferred is not in a billing zone that is charged at a long distance rate.
FIG. 2
presents a message flow for transferring an incoming call (from PSTN
100
) by mobile subscriber
105
to a designated party served by PSTN
100
in accordance with prior art. PSTN
100
uses telephone facility
206
to deliver the incoming call to originating MSC
101
. Originating MSC
101
queries HLR
102
by sending LOCREQ message
207
in order to determine the current location of mobile subscriber
105
to route the call to the appropriate serving MSC
103
. (Message
207
is specified in American National Standards Institute ANSI-41.) Message
207
includes a BILLID parameter equal to O-CALLID to identify the call identification as assigned by originating MSC
101
. Consequently, HLR
102
sends ROUTREQ message
208
(specified in ANSI-41) to serving MSC
103
to determine the preferred method of routing the incoming call to serving MSC
103
. Message
208
contains the BILLID parameter equal to O-CALLID. Serving MSC
103
returns this information using routreq message
209
(specified in ANSI-41). Message
209
contains the BILLID parameter equal to S-CALLID, which is the call identification assigned by serving MSC
103
. Consequently, HLR
102
is able to relate the call identification assigned by originating MSC
101
(O-CALLID) with the call identification assigned by serving MSC
103
(S-CALLID) of the incoming call. Serving MSC
103
establishes a trunk to base station
104
, in which the mobile is located, in preparation for supporting the incoming call. Base station
104
consequently establishes radio connection
212
to mobile subscriber unit
105
.
HLR
102
returns the location of mobile subscriber unit
105
to originating MSC
101
by sending locreq message
211
(specified in ANSI-41). Message
211
contains the BILLID parameter equal to S-CALLID. Originating MSC
101
then establishes a connection to serving MSC
103
through inter-MSC facility
213
. Inter-MSC facility
213
corresponds to inter-MSC facility
108
in FIG.
1
. At this point of time, the incoming call to mobile subscriber unit
105
has been completed.
If mobile subscriber unit
105
wishes to transfer the incoming call to a designated party (and consequently causing mobile subscriber unit
105
to be disconnected from the call), mobile subscriber unit sends call transfer request message
214
to base station
104
. Message
214
is dependent upon the air interface technology, e.g. Advanced Mobile Phone Service (AMPS), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and Groupe Special Mobile (GSM), being supported by base station
104
. (The specific messages for each air interface technology are known to one skilled in the art.) Base station
104
relays this request to serving MSC
103
utilizing facility request message
215
. Messages
214
and
215
contain dialed digits generated by mobile subscriber unit
105
. The dialed digits are interpreted by serving MSC
103
to signify a request for call transfer to a designated party. Serving MSC
103
establishes outgoing facility
216
and connects the incoming call to the designated party. At this point of time, the telephone path consists of telephone facility
206
, inter-MSC facility
213
, and outgoing facility
216
.
Serving MSC
103
initiates the removal of radio connection
212
by sending disconnect message
217
, which in turn causes base station
104
to send disconnect message
218
to mobile subscriber unit
105
. Disconnect message
218
is dependent upon the air interface technology.
In the prior art, the mobile subscriber unit can be afforded call transfer service only if the serving MSC supports call transfer. In other words, even if the originating MSC supports call transfer, the mobile subscriber unit cannot initiate call transfer if the serving MSC does not support it. The present invention does not require the serving MSC to support call transfer in order for the mobile subscriber unit to obtain a call transfer of an incoming call. Moreover, the number of required telephone facilities is reduc
Calabrese Robert Thomas
Smith, Jr. Harold Robert
Zahnle Jeffrey Arthur
Cumming William
Lucent Technologies - Inc.
Santema Steven R.
LandOfFree
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