U.S. patent application number 12/419129 was filed with the patent office on 2009-07-30 for seamless call switching in a dual mode environment.
This patent application is currently assigned to RESEARCH IN MOTION LIMITED. Invention is credited to Gary P. Mousseau, Christopher R. Wormald.
Application Number | 20090191864 12/419129 |
Document ID | / |
Family ID | 34619611 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090191864 |
Kind Code |
A1 |
Mousseau; Gary P. ; et
al. |
July 30, 2009 |
Seamless Call Switching In A Dual Mode Environment
Abstract
Methods and apparatus for providing a seamless switching of
voice calls between different wireless networks are disclosed. In
one illustrative example, a mobile communication device has a
processor and one or more wireless transceivers coupled to the
processor. The one or more wireless transceivers include a first
transceiver portion operative in accordance with a first wireless
network (e.g. a GSM/GPRS cellular network) and a second transceiver
portion operative in accordance with a second wireless network
(e.g. an 802.11 wireless network). A voice call is maintained
between the mobile device and a communication terminal through call
control equipment. The processor of the mobile device is operative
to maintain voice communications for the voice call over a traffic
channel established between the mobile device and the first
wireless network using the first transceiver portion; cause a
connecting call to be established with the communication terminal
through the call control equipment in response to a predetermined
condition, where the connecting call involves a traffic channel
established between the second wireless network and the mobile
device using the second transceiver portion; and after the
connecting call is established, maintain voice communications for
the voice call over the traffic channel established between the
second wireless network and the mobile device.
Inventors: |
Mousseau; Gary P.;
(Waterloo, CA) ; Wormald; Christopher R.;
(Kitchener, CA) |
Correspondence
Address: |
RESEARCH IN MOTION;ATTN: GLENDA WOLFE
BUILDING 6, BRAZOS EAST, SUITE 100, 5000 RIVERSIDE DRIVE
IRVING
TX
75039
US
|
Assignee: |
RESEARCH IN MOTION LIMITED
Waterloo
CA
|
Family ID: |
34619611 |
Appl. No.: |
12/419129 |
Filed: |
April 6, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11669777 |
Jan 31, 2007 |
7526313 |
|
|
12419129 |
|
|
|
|
10992934 |
Nov 19, 2004 |
7187923 |
|
|
11669777 |
|
|
|
|
60523644 |
Nov 20, 2003 |
|
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Current U.S.
Class: |
455/426.1 ;
455/552.1 |
Current CPC
Class: |
H04W 36/0066 20130101;
H04W 36/18 20130101 |
Class at
Publication: |
455/426.1 ;
455/552.1 |
International
Class: |
H04W 4/00 20090101
H04W004/00; H04M 1/00 20060101 H04M001/00 |
Claims
1. A method for use by a mobile communication device in switching a
voice call between two different wireless communication networks,
the method comprising the steps of: maintaining voice
communications for a voice call with a communication terminal
through call control equipment, the voice call involving a traffic
channel established between a first wireless network and the mobile
device with use of a first transceiver portion which operates in
accordance with the first wireless network; causing a connecting
call to be established with the communication terminal through the
call control equipment based on identifying a predetermined
condition, the connecting call involving a traffic channel
established between a second wireless network and the mobile device
using a second transceiver portion which operates in accordance
with the second wireless network; and after the connecting call is
established, maintaining voice communications for the voice call
over the traffic channel established between the second wireless
network and the mobile device.
2. The method of claim 1, wherein one of the first and the second
wireless networks is operative in accordance with a cellular
telecommunications network and the other one of the first and the
second wireless networks is operative in accordance with an 802.11
based wireless network.
3. The method of claim 1, wherein the first wireless network is
operative in accordance with a first cellular telecommunications
network and the second wireless network is operative in accordance
with a second cellular telecommunications network different from
the first cellular telecommunications network.
4. The method of claim 1, wherein the step of causing the
connecting call to be established further comprises: receiving a
call initiation message from the second wireless network for the
connecting call; and causing a call answering message to be sent to
the second wireless network based on receiving the call initiation
message from the second wireless network, for thereby establishing
the traffic channel between the second wireless network and the
mobile device.
5. The method of claim 1, wherein the step of causing the
connecting call to be established further comprises: causing a
network switching message to be sent to the call control equipment;
receiving a call initiation message from the second wireless
network for the connecting call in response to sending the network
switching message to the call control equipment; and causing a call
answering message to be sent to the second wireless network based
on receiving the call initiation message from the second wireless
network, for thereby establishing the traffic channel between the
second wireless network and the mobile device.
6. The method of claim 1, wherein the predetermined condition
comprises one of a poor signal condition with the first wireless
network, a predetermined signal detection from the second wireless
network, and a user input signal at the mobile device.
7. The method of claim 1, wherein the step of causing the
connecting call to be established further comprises: initiating the
connecting call to the call control equipment by sending a call
initiation message to the second wireless network.
8. The method of claim 1, further comprising: causing the traffic
channel with the first wireless network to be terminated after
maintaining the voice communications with the second wireless
network.
9. The method of claim 1, wherein the connecting call comprises a
conference call type connection with the voice call through the
call control equipment.
10. A mobile communication device, comprising: one or more
processors; one or more wireless transceiver coupled to the one or
more processors; the one or more wireless transceivers having a
first transceiver portion operative in accordance with a first
wireless network and a second transceiver portion operative in
accordance with a second wireless network; the one or more
processors being operative to: maintain voice communications for a
voice call with a communication terminal through call control
equipment, the voice call involving a traffic channel established
between the first wireless network and the mobile device with use
of the first transceiver portion; cause a connecting call to be
established with the communication terminal through the call
control equipment based on identifying a predetermined condition,
the connecting call involving a traffic channel established between
the second wireless network and the mobile device with use of the
second transceiver portion; and after the connecting call is
established, maintain voice communications for the voice call over
the traffic channel established between the second wireless network
and the mobile device.
11. The mobile device of claim 10, wherein one of the first and the
second wireless networks is operative in accordance with a cellular
telecommunications network and the other one of the first and the
second wireless networks is operative in accordance with an 802.11
based wireless network.
12. The mobile device of claim 10, wherein the first wireless
network is operative in accordance with a first cellular
telecommunications network and the second wireless network is
operative in accordance with a second cellular telecommunications
network different from the first cellular telecommunications
network.
13. The mobile device of claim 10, wherein the one or more
processors are further operative to cause the connecting call to be
established by: receiving a call initiation message from the second
wireless network for the connecting call; and causing a call
answering message to be sent to the second wireless network based
on receiving the call initiation message from the second wireless
network, for thereby establishing the traffic channel between the
second wireless network and the mobile device.
14. The mobile device of claim 10, wherein the one or more
processors are further operative to cause the connecting call to be
established by: causing a network switching message to be sent to
the call control equipment; receiving a call initiation message
from the second wireless network for the connecting call in
response to sending the network switching message to the call
control equipment; and causing a call answering message to be sent
to the second wireless network based on receiving the call
initiation message from the second wireless network, for thereby
establishing the traffic channel between the second wireless
network and the mobile device.
15. The mobile device of claim 10, wherein the predetermined
condition comprises one of a poor signal condition with the first
wireless network, a predetermined signal detection from the second
wireless network, and a user input signal at the mobile device.
16. The mobile device of claim 10, wherein the one or more
processors are further operative to cause the connecting call to be
established by: initiating the connecting call to the call control
equipment by sending a call initiation message to the second
wireless network.
17. The mobile device of claim 10, wherein the one or more
processors are further operative to cause the connecting call to be
established by: causing the traffic channel with the first wireless
network to be terminated after maintaining the voice communications
with the second wireless network.
18. The mobile device of claim 10, wherein the voice communications
of the voice call comprises Voice over IP (VoIP) communication
through one of the first and the second wireless networks.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of and claims
priority to U.S. non-provisional patent application having
application Ser. No. 11/669,777 and filing date of 31 Jan. 2007,
now U.S. Pat. No. ______, which is a continuation of and claims
priority to U.S. non-provisional patent application having
application Ser. No. 10/992,934 and filing date of 19 Nov. 2004,
now U.S. Pat. No. 7,187,923 B2, which claims priority to U.S.
provisional patent application having application No. 60/523,644
and filing date of 20 Nov. 2004, each application being hereby
incorporated by reference herein.
BACKGROUND
[0002] 1. Field of the Technology
[0003] The present application relates generally to seamlessly
switching between different wireless networks during a voice call
involving a mobile communication device which is compatible with
these wireless networks.
[0004] 2. Description of the Related Art
[0005] In the field of wireless communications, the problem of
seamlessly switching communications between two incompatible
wireless networks for a mobile communication device has not been
adequately addressed.
[0006] One major issue is how to switch between two different
wireless networks without dropping an active call, such as a voice
call, involving the mobile device. In an exemplary situation, the
mobile device may be compatible with both GSM/GPRS technologies and
802.11 technologies but yet be unable to seamlessly switch between
these networks during active calls. This switching would need to
take place without dropping the active call and, preferably,
without letting either party know that the switching has taken
place.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Embodiments of the present application will now be
described, by way of example only, with reference to the attached
figures. Same reference numerals are used in different figures to
denote similar elements.
[0008] FIG. 1 is an illustration of a call control center located
in a carrier's network infrastructure for handling call routing
issues;
[0009] FIG. 2 is an illustration of a call control center located
within a corporation for handling call routing issues;
[0010] FIG. 3 is an illustration of a mobile device roaming away
from an 802.11 hot spot where the call control center located
within a wireless network;
[0011] FIG. 4 is an illustration of a mobile device roaming away
from an 802.11 corporate access point where the call control center
located within the corporation; and
[0012] FIG. 5 is an illustration of a data flow diagram that
supports the mobile device's behaviour when roaming from one
network to another;
[0013] FIG. 6 is a flowchart for describing the mobile device
method of providing the seamless switching of networks for voice
calls;
[0014] FIG. 7 is a flowchart for describing the call control
equipment method of providing the seamless switching of networks
for voice calls involving the mobile device;
[0015] FIG. 8 is an illustration of one of the wireless
communication networks within which the mobile device may
communicate, where the wireless network is a GSM/GPRS based
cellular telecommunications network;
[0016] FIG. 9 is a schematic block diagram of a mobile device in a
specific and preferred implementation as a mobile station; and
[0017] FIG. 10 is a block diagram illustration of pertinent
components of call control equipment for use in the present
application.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Methods and apparatus for providing a seamless switching of
voice calls between different wireless networks are described
herein. In one illustrative example, a mobile communication device
has a processor and one or more wireless transceivers coupled to
the processor. The one or more wireless transceivers include a
first transceiver portion operative in accordance with a first
wireless network (e.g. GSM/GPRS cellular network) and a second
transceiver portion operative in accordance with a second wireless
network (e.g. 802.11 wireless network). Thus, the mobile device is
a dual-mode wireless device. A voice call may be maintained between
the mobile device and a communication terminal through call control
equipment. The processor of the mobile device is operative to
maintain voice communications for the voice call over a traffic
channel established between the mobile device and the first
wireless network using the first transceiver portion; cause a
connecting call to be established with the communication terminal
through the call control equipment in response to a predetermined
condition, where the connecting call involves a traffic channel
established between the second wireless network and the mobile
device using the second transceiver portion; and after the
connecting call is established, maintain voice communications for
the voice call over the traffic channel established between the
second wireless network and the mobile device. In one embodiment,
the one or more processors of the mobile device cause the
connecting call to be established by causing a network switching
message to be sent to the call control equipment; receiving a call
initiation message from the second wireless network for the
connecting call in response to sending the network switching
message; and causing a call answering message to be sent to the
second wireless network based on receiving the call initiation
message from the second wireless network, for thereby establishing
the traffic channel between the second wireless network and the
mobile device.
[0019] Turning to FIG. 1 there is shown a system for handling the
seamless switching of voice calls for a mobile communication device
100. In the embodiment of FIG. 1, call control equipment 112 is
located in a carrier's network infrastructure for handling call
control. The basic architecture for call control equipment 112 is
shown later in relation to FIG. 10. In FIG. 1, mobile device 100 is
shown to operate in a first wireless network 102, which is a wide
area wireless network such as a cellular telecommunications
network. For example, the first wireless network 102 may be a
Global Systems for Mobile Communications (GSM) and General Packet
Radio Service (GPRS) based network. A router 110 routes and
connects outside calls 120 to mobile device 100 with the help of
the subcomponent referred to as the call control equipment 112. In
this embodiment, router 110 resides within, or in close proximity
to, the carrier's network. Router 110 may be a wired or wireless
router and, preferably, router 110 is a wireless router.
[0020] Second wireless network 106 is different from first wireless
network 102; that is, the networks 102 and 106 support different
wireless communication technologies and protocols. To one skilled
in the art, this second wireless network 106 may support one
several different types of networks including cellular networks and
non-cellular networks. These networks may include, but are not
limited to, those based on Code Division Multiple Access (CDMA),
CDMA2000, Universal Mobile Telecommunications Services (UMTS),
iDEN, and Bluetooth. Preferably, however, second wireless network
106 is an 802.11 based network located in a "hot spot". In the
present application, the 802.11 network may be referred to as a
wireless local area network (WLAN). WLANs are typically
wire-connected to the Internet using traditional Telco connections
to provide higher bandwidth data communications for mobile devices.
A WLAN typically operates in accordance with IEEE or ETSI
standards, for example, although any suitable communication
technologies may be utilized. Second wireless network 106 is
connected to a wide area network (WAN) 108, such as the Internet,
to which call control equipment 112 is also connected. Preferably,
second wireless network 106 and mobile device 100 support Voice
over Internet Protocol (VoIP) voice communications. In a primary
embodiment described herein, mobile device 100 maintains a
preference for using second wireless network 106 (i.e. the local
area network or 802.11 WLAN) over first wireless network 102 (i.e.
the wide area cellular network) and attempts to utilize it for
communications whenever possible.
[0021] Mobile device 100 may be on a voice call with a
communication terminal (not shown in FIG. 1) over first wireless
network 102. This voice call is established through or by call
control equipment 112. During the voice call, mobile device 100 may
be moved 104 between first wireless network 102 and a second
wireless network 106. As mobile device 100 reaches second wireless
network 106, it detects the hot spot through coverage indicators
and protocol handshakes, techniques that are well known in the art.
In response, mobile device 100 may send a message 114 to call
control equipment 112 upon entry into the hot spot area. The
message indicates that mobile device 100 has entered within range
of a supportable 802.11 hot spot. The message may further indicate
that the voice call and any data routing mechanism should be
"shifted" to the new network. Alternatively, the transition may be
made by manual user intervention. In any case, if network switching
is performed, cost and speed savings may be achieved by using the
802.11 network instead of the wide-area GSM/GPRS network.
[0022] In an alternate technique, mobile device 100 delays for a
time period during which coverage and/or registration in second
wireless network 106 is maintained before causing the transition.
This time period is monitored with use of a timer. If the
connection with second wireless network 106 fails during this time
period, mobile device 100 refrains from causing any transition
(e.g. refrains from sending the message) and the timer is reset. If
coverage and/or registration with second wireless network 106 is
re-established, mobile device 100 again delays for the timer period
before causing the transition. Preferably, the mobile device delays
for a time period greater than 1 minute. Alternatively, time period
is greater than 30 seconds, such as between about 30 seconds and 2
minutes.
[0023] For transitioning between the networks, call control
equipment 112 silently places a second call to mobile device 100.
This second call involves the communication terminal involved in
the initial voice call with mobile device 100 in a conference call
type connection. As mobile device 100 is expecting this second call
because it initiated the request, mobile device 100 may silently
and seamlessly accept this second call. Mobile device 100 then
switches its audio paths from the first call to the second call.
Preferably, the VoIP communications is utilized in the 802.11 hot
spot area for this call. Note that the transition may be done in a
gradual fashion where audio signals from both calls are first mixed
and gradually increased/decreased in volume until the complete
transition is made; alternatively the transition is abrupt where
there is little if any overlap of the audio. The signal 114 may be
sent over Session Initiation Protocol (SIP) through an IPv6 network
link to call control equipment 112. Alternatively, the solution
operates in connection with traditional technology and data links
available and operating in wireless data networks. Therefore, this
technique requires neither SIP nor IPv6 to operate, although it is
compatible with these technologies if they were present.
[0024] Stability of the new (second) call is ensured over time so
that the original (first) call may be released. That is, the mobile
device 100 delays for a time period during which the second call is
maintained before causing the first call to be released. The time
period is monitored through use of a timer. If the second call
fails during this time period, mobile device 100 maintains the
first call and the timer is reset. If the second call is
reattempted, mobile device 100 again delays for the timer period
before releasing the first call. Preferably, the mobile device
delays for a time period greater than 1 minute. Alternatively, time
period is greater than 30 seconds, such as between about 30 seconds
and 2 minutes.
[0025] The call splitting functionality of call control equipment
112 may be achieved in a few different ways. One known useful
component is provided by OnRelay of the United Kingdom. A
technology component called a Mobile Branch Exchange (MBX) from
OnRelay is a server that resides adjacent to a Public Branch
Exchange (PBX). This MBX takes a copy of an incoming call and rings
a cell phone number at the same time as an associated desk phone,
enabling the end user to pick up the call in either location.
Similarly, for mobile originated calls, the MBX receives the call
information as a Short Message Server (SMS) message, places a call
to the mobile and to the called party, making the called party
think that the call is originating from the user's desk phone. One
feature of the MBX is that a user may be on a mobile device call
and, when the user gets back to his/her desk phone, may pick up the
desk phone and release the mobile device call--similar to switching
phones in the same household. MBX in its current form may handle
either conventional or IP-based PBX systems. It has been developed
solely for use in a PBX environment and routing/bridging calls
between PBXs and mobile phones.
[0026] Other technology components, especially those enabling
mobile "dual-mode" communications and mobile VoIP, may be utilized
to achieve optimized results for the present techniques.
Specifically, optimized features include (1) expanded call control
features, either through SIP or some other mechanism, allowing the
interfacing to an 802.11 network at the same time as controlling a
PBX; alternatively a separate 802.11 access point (AP) could be
used and call control center 112 could interface directly to it;
(2) the presence of dual-mode handsets; (3) a central control and
command infrastructure to access calls and data and to route to
either network as necessary; (4) communicating `out-of-band` to the
mobile device 100 while maintaining a phone call. Specifically, for
example, Qualcomm announced the implementation of both WCDMA
(a.k.a. UMTS) and GSM calls with a mobile device using a
radioOne.TM. direct conversion RF dual-mode solution technology.
The mobile device utilized an integrated MSM6200.TM. Mobile Station
Modem (MSM.TM.) chipset solution, consisting of the MSM6200
UMTS/GSM/GPRS baseband modem, RFL6200.TM. and RFR620.TM. WCDMA
receivers, RTR6200.TM. GSM transceiver with WCDMA transmitter, and
PM6050.TM. power management device. In addition, a company called
Spectralink of Boulder, Colo., U.S.A., makes Voice over IP (VoIP)
telephony technology using 802.11-based handset phones. This
technology component allows owners of traditional PBX phone systems
in an enterprise business take advantage of VoIP phones. A NetLink
PRI Gateway connects to PBX phone systems that have a trunked ISDN
primary rate interface (PRI) so it may support several mobile
devices simultaneously. The gateway, in turn, connects to the wired
network and on to the access points (APs) that talk to the VoIP
handsets.
[0027] Turning now to FIG. 2, there is shown an illustration of
call control center 112 being located within a corporation 124. A
second wireless network 118 within or adjacent corporation 124 is a
wireless 802.11 LAN sometimes termed a "Wi-Fi" network. These
wireless LAN solutions are now commonly supported within such
corporations 124. Companies are currently using wireless LAN
solutions to support the campus-wide demand for an Intranet 122
within corporation 124. Once connected to the Intranet 122, access
to company resources becomes possible. Naturally, the second
wireless network 118 is seen as bridging a firewall 116 protection
of the corporation 124 (if any), most corporations are currently
addressing these security problems today where applicable.
[0028] An initial voice call is either received or placed by mobile
device 100. For calls placed from mobile device 100, the desire to
place a call is signalled to call control equipment 112, which then
simultaneously places the voice call to mobile device 100 and the
communication terminal that the end user of mobile device 100
desires to call. In this way, call control equipment 112 retains
control of the voice call at all times. As mobile device 100 moves
from first wireless network 102 (e.g. GSM/GPRS) to second wireless
network 118 (e.g. 802.11 wireless LAN), the voice call is initially
maintained in GSM/GPRS. Note that the 802.11 transceiver portion on
mobile device 100 operates independently of the GSM/GPRS
transceiver portion on the same mobile device 100.
[0029] Next, mobile device 100 uses 802.11 to send a signal 114
through second wireless network 118. Signal 114 instructs call
control equipment 112 to place another call to mobile device 100
through the 802.11 network. This second call involves the
communication terminal involved in the initial voice call with
mobile device 100 in a conference call type connection. Thus, as
mobile device 100 moves onto campus and locks onto second wireless
network 118, mobile device 100 messages call control equipment 112
to place the second call to mobile device 100 over second wireless
network 118. Call control equipment 112 may either perform this
function directly or request the PBX to connect the additional
call, depending on the specific design of call control equipment
112. Once mobile device 100 has the new call, it merges it with the
existing voice call, performs a final check to ensure that the new
call is of adequate quality, and then terminates the GSM/GPRS
call.
[0030] As described, this changeover may be performed automatically
by mobile device 100 with or without being governed by algorithms
that detect a "constant and clean" 802.11 signal corresponding to
second wireless network 118. For example, if a signal is detected
that has a signal quality of `X`, for a period of `N` minutes, then
the second call may be warranted. Thus, mobile device 100 delays
for a time period during which coverage and/or registration in
second wireless network 118 is maintained before causing the
transition. This time period is monitored with use of a timer. If
the connection with second wireless network 118 fails during this
time period, mobile device 100 refrains from causing any transition
(e.g. refrains from sending the message) and the timer is reset. If
coverage and/or registration with second wireless network 118 is
reestablished, mobile device 100 again delays for the timer period
before causing the transition. Preferably, the mobile device delays
for a time period greater than 1 minute. Alternatively, time period
is greater than 30 seconds, such as between about 30 seconds and 2
minutes. Using an alternative technique, no automatic transitioning
is performed by mobile device 100 but rather mobile device 100
visually displays an option for or choice between networks for the
end user. The end user may select the new second network which
causes the transition.
[0031] Either mobile device 100 or call control equipment 112 may
control the process of determining at what point in time to drop
the merged call. In one embodiment, mobile device 100 is better
situated to determine how long to hold the two calls and to
understand the conditions needed to be able to drop the first call.
In another embodiment, there is greater elegance for call control
equipment 112 to handle dropping the initial call, for example, by
maintaining a timer. Once the second call is primary to mobile
device 100, call control center 112 may seamlessly drop the
original call portion. Thus, stability of the new (second) call is
ensured over time so that the original (first) call may be
released. That is, the mobile device 100 delays for a time period
during which the second call is maintained before causing the first
call to be released. The time period is monitored through use of a
timer. If the second call fails during this time period, mobile
device 100 maintains the first call and the timer is reset. If the
second call is reattempted, mobile device 100 again delays for the
timer period before releasing the first call. Preferably, the
mobile device delays for a time period greater than 1 minute.
Alternatively, time period is greater than 30 seconds, such as
between about 30 seconds and 2 minutes.
[0032] Turning now to FIG. 3, there is shown an illustration of
mobile device 100 heading away from an 802.11 hot spot where call
control center 112 is located within second wireless network 106.
All elements of the solution are identical to FIG. 1, except for
mobile device 100 is now moving away from the 802.11 hotspot. This
scenario is more complicated then that described in relation to the
previous figures as mobile device 100 is slowing losing coverage
and voice quality. Mobile device 100 maintains 802.11 coverage as
long as possible, as this is the cheapest and fastest communication
method. As coverage fails, mobile device 100 may send a signal to
call control equipment 112 automatically or through a user request.
Mobile device 100 uses first wireless network 102 (GSM/GPRS) to
send signal 114 as this should be more reliable. Call control
equipment 112 then places a second call to mobile device 100 over
first wireless network 102. This second call involves the
communication terminal involved in the initial voice call with
mobile device 100 in a conference call type connection. As
described in relation to the previous figures, mobile device 100
quietly receives this second call, and may merge the two calls
similar to a conference call connection. Shortly thereafter, the
first call is dropped and the user is left with the call through
first wireless network 102. Note that, in this embodiment, it is
possible that the end user might have to force early termination of
the first call if static and voice quality drops too quickly. This
could result in a small delay or detection by the other party that
a transition has occurred.
[0033] Turning now to FIG. 4, there is shown an illustration of
mobile device 100 heading away from an 802.11 corporate access
point (AP) where call control center 112 is located within the
corporation 124. The elements shown in FIG. 4 are similar to FIG. 2
except that mobile device 100 is moving away from second wireless
network 118. In this scenario, mobile device 100 detects a reduced
signal from second wireless network 118, or the user invokes a menu
that allows them to control network switching (e.g. they realize
they are leaving the 802.11 campus area). As in FIG. 3, signal 114
is communicated over the first wireless network 102 as the
reliability should be higher. When the message is received by call
control equipment 112, it issues a second call over first wireless
network 102 to mobile device 100. This second call involves the
communication terminal involved in the initial voice call with
mobile device 100 in a conference call type connection. Mobile
device 100 then answers the call, preferably silently without
disruption, and merges the two calls similar to a conference call.
After a period of time (e.g. in the range of seconds or less),
mobile device 100 or call control equipment 112 drops the original
call in favor of the second call over first wireless network
102.
[0034] A voice call 120 may also be received on or placed to mobile
device 100 using a voice over IP (VoIP) method on the 802.11
network 118. Call control equipment 112 retains control of the
voice call 120 at all times. As the caller's connection to second
wireless network 118 starts to fade (or a handover is initiated by
the caller through the push of a button on the mobile device 100),
mobile device 100 signals 114 through second wireless network 118
to instruct call control equipment 112 to initiate a call over
first wireless network 102. Mobile device 100, with knowledge that
an incoming call is imminent and the number the call is coming
from, silently accepts the call and authenticates it as a handover
of the current call over second wireless network 118. From here,
the two calls are merged (similar to a conference call). Once its
confirmed that the new call is stable and ready, mobile device 100
or call control equipment 112 drops the 802.11 call, and the new
GSM/GPRS call is maintained. Neither party on the phone detects any
mode change taking place assuming both 802.11 quality of service is
acceptable and GSM/GPRS reception is good. Note that there is
always at least one call session active on mobile device 100 at any
given point of time.
[0035] In an alternative embodiment, where mobile device 100 hits a
dramatic "falling off" of 802.11 coverage, call control equipment
112 intervenes and automatically switches the call over first
wireless network 102 (GSM/GPRS). In this situation, call control
equipment 112 may notice that data intended for mobile device 100
fails to be delivered, or that the call has been dropped on the
802.11 network. In this case, the call is automatically moved over
to the wide-area GSM/GPRS network for recovery. To assist with
interruption, call control equipment 112 may inform the other party
by audio that they will be reconnected momentarily while initiating
an outbound GSM/GPRS connection to mobile device 100.
Alternatively, mobile device 100 may initiate the resumption of the
call over GSM/GPRS by detecting the unintentional loss of the
802.11 call and immediately sending a "resume" call packet over the
GSM/GPRS network to call control equipment 112. This message may be
a simple datagram using proprietary protocols or a SIP-based
message as already discussed.
[0036] Turning to FIG. 5, there is shown an illustration of a data
flow diagram supporting the mobile device's behavior when moving
from one network to another. In step 200, the user and mobile
device are moving and eventually a transition stage is reached.
This is a stage where mobile device is in coverage of two different
networks. If the user detects a change (step 202), perhaps either
in voice quality or by knowledge of an alternative network option,
they may act on such situations. The alternative network could be a
less expensive option like 802.11 or Bluetooth, or they might be
leaving an 802.11 network shortly and want to return to their
wide-area GSM/GPRS network connection. If the user desires to
change the network, the user may invoke a menu and request the
network change directly through the user interface (step 204).
[0037] If the mobile device detects a change in step 204, either
through reduced coverage parameters, or in the arrival of a new
network connection with higher priority, it may decide to make a
change. A network may have a different priority due to a better
cost or speed. If the mobile device does not detect that a change
is needed or possible in step 204, then it is loss of the call that
determines that something must be done. When the call is dropped in
step 208, either the user acts on the problem or the call control
equipment detects the problem and acts. If the user detects the
call is lost and decides to act at step 208, the user may select a
menu item on the mobile device to request the call be re-routed to
an alternative network (step 210). In an exemplary situation, the
user has just left an 802.11 network and coverage on the wide-area
GSM/GPRS network was initially too weak to support a call. Then,
within seconds, the coverage improves and the call is routed to the
mobile device before the other party drops off.
[0038] If the call control equipment detects that the call has
dropped in step 208, it places a call to the mobile device to open
a new call through an alternative network connection (step 212). If
configured and selected by the user, a message may be played for
the other caller (step 214). When the call is completed the calls
are bridged or connected together (step 215). Referring back to the
step 206, where the mobile device detects the change in network
coverage, or after the user selects a menu to change networks at
steps 204 and 210, a signal is next sent to the call control
equipment (step 216). In response, the call control equipment
bridges or connects the calls together (step 218), similar to a
conference call connection. After a certain length of time during
which the new call is stable, the first call is dropped (step
220).
[0039] FIG. 6 is a flowchart which describes a method for use by a
mobile communication device in switching voice calls between two
different wireless communication networks. This method may be
performed in the environment(s) described in relation to FIGS. 1-4,
with the mobile device shown and described later in relation to
FIGS. 9-10. Note that although the method describes the transition
from a first wireless network to a second wireless network, the
same or similar techniques may be utilized for transitioning from
the second wireless network to the first wireless network. The
steps are performed by one or more controllers or processors (e.g.
a microprocessor and/or DSP) of the mobile device, in connection
with any other necessary device components (e.g. its RF transceiver
portions). As apparent from this method description, the call
control equipment performs a complimentary method (see FIG. 7)
associated with the mobile device method. A computer program
product of the present application may include a storage medium
(e.g. FLASH memory) and computer instructions stored in the storage
medium which are executed by the one or more processors for
performing such methods. In this method, the mobile device has a
first transceiver portion which operates in accordance with a first
wireless network (e.g. GSM/GPRS cellular network) and a second
transceiver portion which operates in accordance with a second
wireless network (e.g. 802.11 wireless network). Preferably, Voice
over IP (VoIP) communications is utilized through one of the
wireless networks (e.g. the 802.11 network) for a lower cost
alternative. Note further that the mobile device may be associated
with at least two different unique identifiers (e.g. telephone
number, mobile telephone number, and/or IP address) for
implementing the method. As an example, the mobile device may
publish or provide only a corporate enterprise telephone number for
others to contact the mobile device. When dialled by an outside
caller, this telephone number call always gets routed to the call
control equipment, which causes the mobile device to be alerted to
the incoming call within the enterprise (e.g. the call control
equipment using the telephone number or IP address of the mobile
device via the 802.11 network) and/or outside the enterprise (e.g.
the call control equipment using the mobile telephone number of the
mobile device via the cellular network).
[0040] Beginning at a start block 602 of FIG. 6, the mobile device
maintains voice communications for a voice call established between
the mobile device and a communication terminal through the first
wireless network (step 604 of FIG. 6). This call is facilitated
through the call control equipment. From the perspective of the
mobile device, the voice call involves one or more traffic channels
established between the first wireless network and the mobile
device using the first transceiver portion. During the voice call,
the mobile device causes a connecting call to be established with
the call control equipment (step 606 of FIG. 6). This connecting
call involves the communication terminal involved in the initial
voice call with the mobile device in a conference call type
connection. In addition, the connecting call involves one or more
traffic channels established between the second wireless network
and the mobile device using the second transceiver portion.
Subsequently, the mobile device maintains voice communications for
the voice call over the traffic channel established between the
second wireless network and the mobile device (step 608 of FIG. 6).
Note that the call control equipment causes the voice
communications of the voice call through the first wireless network
to be replicated in the connecting call through the second wireless
network, so that the mobile device simultaneously maintains the
voice communications for the voice call through both the first and
the second wireless networks.
[0041] The mobile device may cause the connecting call of step 606
to be established in a number of different ways. In one embodiment,
the mobile device initially causes a network switching message to
be sent to the call control equipment upon detection of a
predetermined condition. In this case, the mobile device
subsequently receives a call initiation message (e.g. a page
message for a call) from the second wireless network for the
connecting call that is sent in response to the network switching
message. In response to the call initiation message, the mobile
device answers the connecting call by causing a call answering
message (e.g. a page response message) to be sent to the second
wireless network, which thereby establishes the one or more traffic
channels between the second wireless network and the mobile device.
In an alternative embodiment, the call control equipment initiates
the connecting call without the need to receive any network
switching message from the mobile device. In yet another
alternative embodiment, the mobile device is the entity that
initiates the connecting call to the call control equipment by
sending a call initiation message to the second wireless network,
where the call control equipment automatically answers the
connecting call.
[0042] Either way, the mobile device "automatically" and "silently"
performs the activities necessary in step 606 of FIG. 6 for calling
or answering the connecting call. Put another way, the activities
in step 606 may be performed by the mobile device so as to be
transparent to the end user. Alternatively, the mobile device may
cause a user input prompt to be visually displayed in its visual
display (or invoke a "call ringing" at the mobile device) for end
user selection of whether the alternative (second) wireless network
should be utilized. If the alternative wireless network is selected
by the end user, the mobile device causes the connecting call to be
established with the call control equipment. If the alternative
wireless network is not selected by the end user, the mobile device
does not cause the connecting call to be established with the call
control equipment (i.e. the mobile device remains on the first
wireless network).
[0043] As indicated earlier, the connecting call of step 606 may be
established in response to identifying a predetermined condition.
The predetermined condition may be, for example, a poor signal
condition between the mobile device and the first wireless network
(e.g. the 802.11 wireless network). As another example, the
predetermined condition may be a predetermined signal detection of
the second wireless network (e.g the local area 802.11 wireless
network). That is, the mere detection of the availability of the
second wireless network may be sufficient for the establishment of
the connecting call with the call control equipment. As yet another
example, the predetermined condition may be a user input signal
detected at the mobile device. Specifically, the mobile device may
visually display a user input prompt or an option (e.g. pop-up
input prompt) for the end user to select the alternative (second)
wireless network when it becomes available; the end user selection
of this option is the user input signal which triggers the
connecting call to the call control equipment. Note that the
predetermined condition is preferably identified and acted upon at
the mobile device, but may alternatively be identified and acted
upon at the call control equipment.
[0044] The mobile device may delay for a time period during which
coverage and/or registration in second wireless network (e.g.
802.11) is maintained before causing the transition. This time
period is monitored with use of a timer. If the connection with
second wireless network fails during this time period, the mobile
device refrains from causing any transition (e.g. refrains from
sending the message) and the timer is reset. If coverage and/or
registration with second wireless network is re-established, the
mobile device again delays for the timer period before causing the
transition. Preferably, the mobile device delays for a time period
greater than 1 minute. Alternatively, time period is greater than
30 seconds, such as between about 30 seconds and 2 minutes.
Similarly, stability of the new (second) call may be ensured over
time so that the original (first) call may be released. That is,
the mobile device delays for a time period during which the second
call is maintained before causing the first call to be released.
The time period is monitored through use of a timer. If the second
call fails during this time period, the mobile device maintains the
first call and the timer is reset. If the second call is
reattempted, the mobile device again delays for the timer period
before releasing the first call. Preferably, the mobile device
delays for a time period greater than 1 minute. Alternatively, time
period is greater than 30 seconds, such as between about 30 seconds
and 2 minutes.
[0045] Depending on the specific implementation, at some point in
time the mobile device may completely switch its audio paths
(speaker and microphone) from the one or more traffic channels with
the first wireless network to the one or more traffic channels with
the second wireless network. This may be done in a quick and abrupt
fashion or, alternatively, in a gradual fashion where the audio
signals of both calls are first mixed and then subsequently
gradually decreased in volume (to/from the first wireless network)
and correspondingly increased in volume (to/from the second
wireless network) until fully switched. Such techniques may be
performed by the mobile device or alternatively by the call control
equipment. At some point in time, the mobile device may cause the
connection portion of the voice call from the call control
equipment to the mobile device through the first wireless network
to be terminated. When this happens, the one or more traffic
channels with the first wireless network are terminated. This may
be done by sending a suitable message to the call control
equipment, for example, through the first wireless network.
Alternatively, the call control equipment may initiation the
termination of the connection portion of the original call.
[0046] FIG. 7 is a flowchart which describes a method for use by
call control equipment in switching voice calls for a mobile device
between two different wireless networks. This method may be
performed in the environment(s) described in relation to FIGS. 1-4.
Note that although the method describes the transition from a first
wireless network to a second wireless network, the same or similar
techniques may be utilized for transitioning from the second
wireless network to the first wireless network. The steps are
performed by computer instructions executed by one or more
controllers or processors (e.g. a microprocessor) of a call control
server of the call control equipment. The basic architecture for
call control equipment 112 is shown later in relation to FIG. 10.
As apparent from this method description, the mobile device
performs a complimentary method (see FIG. 6) associated with the
call control method. A computer program product of the present
application may include a storage medium (e.g. memory) and computer
instructions stored in the storage medium which are executed by the
one or more processors for performing such methods. Preferably,
Voice over IP (VoIP) communications is utilized through one of the
wireless networks (e.g. the 802.11 network) for a lower cost
alternative. Note that the mobile device may be associated with at
least two different unique identifiers (e.g. telephone number,
mobile telephone number, and/or IP address) for the method. As an
example, the mobile device may publish or provide only a corporate
enterprise telephone number for others to contact the device. When
dialled, this telephone number always gets routed to the call
control equipment which causes the mobile device to be alerted to
the incoming call within the enterprise (e.g. with use of the
telephone number or IP address of the mobile device via the 802.11
network) and/or outside the enterprise (e.g. with use of the mobile
telephone number of the mobile device via the cellular
network).
[0047] Beginning at a start block 702 of FIG. 7, the call control
equipment facilitates the establishment of a voice call between the
mobile device and a communication terminal through the first
wireless network (step 704 of FIG. 7). From the perspective of the
mobile device, the voice call involves one or more traffic channels
established between the first wireless network and the mobile
device. During the voice call, the call control equipment causes a
connecting call to be established with the mobile device (step 706
of FIG. 7). This connecting call involves the communication
terminal involved in the initial voice call with the mobile device
in a conference call type connection. In addition, the connecting
call involves one or more traffic channels established between the
second wireless network and the mobile device. The call control
equipment connects or bridges the connecting call with the voice
call so that voice communications may be maintained over the
traffic channel between the second wireless network and the mobile
device (step 708 of FIG. 7). In particular, the call control
equipment causes the voice communications of the voice call through
the first wireless network to be replicated in the connecting call
through the second wireless network, so that the mobile device
simultaneously maintains the voice communications for the voice
call through both the first and the second wireless networks. Thus,
two simultaneous voice communication paths of the voice call for
the mobile device are maintained by the call control equipment.
[0048] The call control equipment may cause the connecting call of
step 706 to be established in a number of different ways. In one
embodiment, the mobile device initially causes a network switching
message to be sent to the call control equipment upon detection of
a predetermined condition. In response, the call control equipment
initiates the connecting call to the mobile device which causes the
second wireless network to send a call initiation message (e.g. a
page message for a call) to the mobile device. In response to the
call initiation message, the mobile device answers the connecting
call by causing a call answering message (e.g. a page response
message) to be sent to the second wireless network. In an
alternative embodiment, the call control equipment initiates the
connecting call without the need to receive any network switching
message from the mobile device. In yet another alternative
embodiment, the mobile device is the entity that initiates the
connecting call to the call control equipment by sending a call
initiation message to the second wireless network, where the call
control equipment automatically answers the connecting call.
[0049] Either way, the call control equipment and mobile device
"automatically" and "silently" perform the activities necessary in
step 706 of FIG. 7 for calling or answering the connecting call.
Put another way, the activities in step 706 may be performed so as
to be transparent to the end user of the mobile device.
Alternatively, the mobile device may cause a user input prompt to
be visually displayed in its visual display (or invoke a "call
ringing" at the mobile device) for end user selection of whether
the alternative (second) wireless network should be utilized. If
the alternative wireless network is selected by the end user, the
mobile device causes the connecting call to be established with the
call control equipment. If the alternative wireless network is not
selected by the end user, the mobile device does not cause the
connecting call to be established with the call control equipment
(i.e. the mobile device remains on the first wireless network).
[0050] As indicated earlier, the connecting call of step 706 may be
established in response to identifying a predetermined condition.
The predetermined condition may be, for example, a poor signal
condition between the mobile device and the wireless network (e.g.
802.11 network). As another example, the predetermined condition
may be a predetermined signal detection of the wireless network
(e.g. 802.11 network). That is, the mere detection of the
availability of the second wireless network may be sufficient for
the establishment of the connecting call with the call control
equipment. As yet another example, the predetermined condition may
be a user input signal detected at the mobile device. Specifically,
the mobile device may visually display a user input prompt or an
option for the end user to select the alternative (second) wireless
network when it becomes available; the end user selection of this
option is the user input signal which triggers the connecting call
to the call control equipment. Note that the predetermined
condition is preferably identified and acted upon at the mobile
device, but may alternatively be identified and acted upon at the
call control equipment.
[0051] At some point in time, the call control equipment may
completely switch the audio paths (both receive and transmit paths)
from the original voice call (i.e. through the first wireless
network) to the connecting call (i.e. through the second wireless
network). This may be done in a quick and abrupt fashion or,
alternatively, in a gradual fashion where the audio signals of both
calls are first mixed and then subsequently gradually decreased in
volume (to/from the first wireless network) and correspondingly
increased in volume (to/from the second wireless network) until
fully switched. Such techniques may be performed by the call
control equipment or alternatively by the mobile device.
Thereafter, the connection portion of the voice call from the call
control equipment to the mobile device through the first wireless
network is terminated. When this happens, the one or more traffic
channels with the first wireless network are terminated. The call
control equipment may, for example, initiate the termination of the
connection portion of the original call.
[0052] FIG. 8 is a block diagram of a communication system 800
which includes a mobile communication device 802. Mobile device 802
may be utilized in the techniques of the present application as
described above. As shown, mobile device 802 is adapted to
communicate with a wireless local area network (WLAN) 890. Also as
shown, mobile device 802 is adapted to communicate with a wireless
communication network 104 which is a cellular telecommunications
network. In the embodiment shown in FIG. 8, wireless network 804 is
configured in accordance with General Packet Radio Service (GPRS)
and a Global Systems for Mobile (GSM) technologies. However, any
suitable type of network communication protocols may be utilized.
For example, the network may be based on code division multiple
access (CDMA) or other suitable technologies. As another example,
the network may be based on an Integrated Dispatch Enhanced Network
(iDEN) which is a high-capacity digital trunked radio system
providing integrated voice and data services.
[0053] For wireless communication with wireless network 804, mobile
device 802 utilizes radio frequency (RF) transceiver circuitry 808a
and an antenna 810a. For wireless communication with WLAN 890,
mobile device 802 utilizes RF transceiver circuitry 808b and an
antenna 810b. With such configuration, mobile device 802 may be
referred to as a "dual mode" communication device. Although shown
in FIG. 8 as having separate and independent transceiver
components, at least some portions or components of these otherwise
different transceivers may be shared where possible.
[0054] In the embodiment shown, mobile device 802 includes a visual
display 812, a keyboard 814, and perhaps one or more auxiliary user
interfaces (UI) 816, each of which are coupled to a controller 806.
Controller 806 is further coupled to radio frequency (RF)
transceiver circuitry 808a and an antenna 810a, as well as to RF
transceiver circuitry 808b and an antenna 810b. Typically,
controller 806 is embodied as a central processing unit (CPU) which
runs operating system software in a memory component (not shown).
Controller 806 will normally control overall operation of mobile
device 802, whereas signal processing operations associated with
communication functions are typically performed in the RF
transceiver circuitry. Controller 806 interfaces with device
display 812 to display received information, stored information,
user inputs, and the like. Keyboard 814, which may be a telephone
type keypad or full alphanumeric keyboard, is normally provided for
entering data for storage in mobile device 802, information for
transmission to network 804, a telephone number to place a
telephone call, commands to be executed on mobile device 802, and
possibly other or different user inputs.
[0055] Mobile device 802 sends communication signals to and
receives communication signals over wireless links. For
communication with wireless network 804, RF transceiver circuitry
808a performs functions similar to those of base station 818 and
base station controller 820, including for example
modulation/demodulation and possibly encoding/decoding and
encryption/decryption. It is also contemplated that RF transceiver
circuitry 808a may perform certain functions in addition to those
performed by base station controller 820. It will be apparent to
those skilled in art that RF transceiver circuitry 808a will be
adapted to particular wireless network or networks in which mobile
device 802 is intended to operate.
[0056] Mobile device 802 includes a battery interface 834 for
receiving one or more rechargeable batteries 832. Battery 832
provides electrical power to electrical circuitry in mobile device
802, and battery interface 834 provides for a mechanical and
electrical connection for battery 832. Battery interface 834 is
coupled to a regulator 836 which regulates power to the device.
When mobile device 802 is fully operational, an RF transmitter of
RF transceiver circuitry 808a is typically keyed or turned on only
when it is sending to network, and is otherwise turned off to
conserve resources. Similarly, an RF receiver of RF transceiver
circuitry 808a is typically periodically turned off to conserve
power until it is needed to receive signals or information (if at
all) during designated time periods.
[0057] Mobile device 802 operates using a Subscriber Identity
Module (SIM) 840 which is connected to or inserted in mobile device
802 at a SIM interface 842. SIM 840 is one type of a conventional
"smart card" used to identify an end user (or subscriber) of mobile
device 802 and to personalize the device, among other things.
Without SIM 840, the mobile device terminal is not fully
operational for communication through wireless network 804. By
inserting SIM 840 into mobile device 802, an end user may have
access to any and all of his/her subscribed services. SIM 840
generally includes a processor and memory for storing information.
Since SIM 840 is coupled to SIM interface 842, it is coupled to
controller 806 through communication lines 844. In order to
identify the subscriber, SIM 840 contains some user parameters such
as an International Mobile Subscriber Identity (IMSI). An advantage
of using SIM 840 is that end users are not necessarily bound by any
single physical mobile device. SIM 840 may store additional user
information for the mobile device as well, including datebook (or
calendar) information and recent call information.
[0058] Mobile device 802 may consist of a single unit, such as a
data communication device, a cellular telephone, a
multiple-function communication device with data and voice
communication capabilities, a personal digital assistant (PDA)
enabled for wireless communication, or a computer incorporating an
internal modem. Alternatively, mobile device 802 may be a
multiple-module unit comprising a plurality of separate components,
including but in no way limited to a computer or other device
connected to a wireless modem. In particular, for example, in the
mobile device block diagram of FIG. 8, RF transceiver circuitry
808a and antenna 810a may be implemented as a radio modem unit that
may be inserted into a port on a laptop computer. In this case, the
laptop computer would include display 812, keyboard 814, one or
more auxiliary UIs 816, and controller 806 embodied as the
computer's CPU. It is also contemplated that a computer or other
equipment not normally capable of wireless communication may be
adapted to connect to and effectively assume control of RF
transceiver circuitry 808a and antenna 810a of a single-unit device
such as one of those described above. Such a mobile device 802 may
have a more particular implementation as described later in
relation to the mobile device of FIG. 9.
[0059] Using RF transceiver circuitry 808a, mobile device 802
communicates in and through wireless communication network 804. In
the embodiment of FIG. 8, wireless network 804 is configured in
accordance with GSM and GPRS technologies. Wireless network 804
includes a base station controller (BSC) 820 with an associated
tower station 818, a Mobile Switching Center (MSC) 822, a Home
Location Register (HLR) 832, a Serving GPRS Support Node (SGSN)
826, and a Gateway GPRS Support Node (GGSN) 828. MSC 822 is coupled
to BSC 820 and to a landline network, such as a Public Switched
Telephone Network (PSTN) 824. SGSN 826 is coupled to BSC 820 and to
GGSN 828, which is in turn coupled to a public or private data
network 830 (such as the Internet). HLR 832 is coupled to MSC 822,
SGSN 826, and GGSN 828.
[0060] Station 818 is a fixed transceiver station, and station 818
and BSC 820 are together referred to herein as the fixed
transceiver equipment. The fixed transceiver equipment provides
wireless network coverage for a particular coverage area commonly
referred to as a "cell". The fixed transceiver equipment transmits
communication signals to and receives communication signals from
mobile devices within its cell via station 818. The fixed
transceiver equipment normally performs such functions as
modulation and possibly encoding and/or encryption of signals to be
transmitted to the mobile device in accordance with particular,
usually predetermined, communication protocols and parameters,
under control of its controller. The fixed transceiver equipment
similarly demodulates and possibly decodes and decrypts, if
necessary, any communication signals received from mobile device
802 within its cell. Communication protocols and parameters may
vary between different networks. For example, one network may
employ a different modulation scheme and operate at different
frequencies than other networks.
[0061] For all mobile device's 802 registered with a network
operator, permanent data (such as mobile device 802 user's profile)
as well as temporary data (such as mobile device's 802 current
location) are stored in HLR 832. In case of a voice call to mobile
device 802, HLR 832 is queried to determine the current location of
mobile device 802. A Visitor Location Register (VLR) of MSC 822 is
responsible for a group of location areas and stores the data of
those mobile devices that are currently in its area of
responsibility. This includes parts of the permanent mobile device
data that have been transmitted from HLR 832 to the VLR for faster
access. However, the VLR of MSC 822 may also assign and store local
data, such as temporary identifications. Optionally, the VLR of MSC
822 may be enhanced for more efficient co-ordination of GPRS and
non-GPRS services and functionality (e.g. paging for
circuit-switched calls which may be performed more efficiently via
SGSN 826, and combined GPRS and non-GPRS location updates).
[0062] SGSN 826 is at the same hierarchical level as MSC 822 and
keeps track of the individual locations of mobile devices. SGSN 826
also performs security functions and access control. GGSN 828
provides interworking with external packet-switched networks and is
connected with SGSNs (such as SGSN 826) via an IP-based GPRS
backbone network. SGSN 826 performs authentication and cipher
setting procedures based on the same algorithms, keys, and criteria
as in existing GSM. In conventional operation, cell selection may
be performed autonomously by mobile device 802 or by the fixed
transceiver equipment instructing mobile device 802 to select a
particular cell. Mobile device 802 informs wireless network 804
when it reselects another cell or group of cells, known as a
routing area.
[0063] In order to access GPRS services, mobile device 802 first
makes its presence known to wireless network 804 by performing what
is known as a GPRS "attach". This operation establishes a logical
link between mobile device 802 and SGSN 826 and makes mobile device
802 available to receive, for example, pages via SGSN,
notifications of incoming data, or SMS messages over GPRS. In order
to send and receive GPRS data, mobile device 802 assists in
activating the packet data address that it wants to use. This
operation makes mobile device 802 known to GGSN 828; interworking
with external data networks may thereafter commence. User data may
be transferred transparently between mobile device 802 and the
external data networks using, for example, encapsulation and
tunneling. Data packets are equipped with GPRS-specific protocol
information and transferred between mobile device 802 and GGSN
828.
[0064] FIG. 9 is a more detailed diagram of a preferred mobile
device of FIG. 8, namely a mobile station 902. Mobile station 902
is preferably a two-way communication device having at least voice
and advanced data communication capabilities, including the
capability to communicate with other computer systems. Depending on
the functionality provided by mobile station 902, it may be
referred to as a data messaging device, a two-way pager, a cellular
telephone with data messaging capabilities, a wireless Internet
appliance, or a data communication device (with or without
telephony capabilities).
[0065] As shown in FIG. 9, mobile station 902 is adapted to
wirelessly communicate with WLAN 992. Also as shown, mobile station
902 is adapted to wirelessly communicate with cellular base station
transceiver systems 900. For communication with cellular networks,
mobile station 902 utilizes a communication subsystem 911. For
communication with WLANs, mobile station 902 utilizes an additional
communication subsystem 990 which has the same structural
components as communication subsystem 911. With such configuration,
mobile station 902 may be referred to as a "dual mode" mobile
station. Although shown in FIG. 9 as having separate and
independent subsystems, at least some portions or components of
these otherwise different subsystems may be shared where
possible.
[0066] Communication subsystem 911, which includes a receiver 912,
a transmitter 914, and associated components, such as one or more
(preferably embedded or internal) antenna elements 916 and 918,
local oscillators (LOs) 913, and a processing module such as a
digital signal processor (DSP) 920. Communication subsystem 911 is
analogous to RF transceiver circuitry 808a and antenna 810a shown
in FIG. 8. As will be apparent to those skilled in field of
communications, particular design of communication subsystem 911
depends on the communication network in which mobile station 902 is
intended to operate.
[0067] Mobile station 902 may send and receive communication
signals over the cellular network after required network procedures
have been completed. Signals received by antenna 916 through the
network are input to receiver 912, which may perform such common
receiver functions as signal amplification, frequency down
conversion, filtering, channel selection, and like, and in example
shown in FIG. 9, analog-to-digital (A/D) conversion. A/D conversion
of a received signal allows more complex communication functions
such as demodulation and decoding to be performed in DSP 920. In a
similar manner, signals to be transmitted are processed, including
modulation and encoding, for example, by DSP 920. These
DSP-processed signals are input to transmitter 914 for
digital-to-analog (D/A) conversion, frequency up conversion,
filtering, amplification and transmission over communication
network via antenna 918. DSP 920 not only processes communication
signals, but also provides for receiver and transmitter control.
For example, the gains applied to communication signals in receiver
912 and transmitter 914 may be adaptively controlled through
automatic gain control algorithms implemented in DSP 920.
[0068] For communications with a cellular network, network access
is associated with a subscriber or user of mobile station 902, and
therefore mobile station 902 requires a Subscriber Identity Module
or "SIM" card 962 to be inserted in a SIM interface 964 in order to
operate in the network. SIM 962 includes those features described
in relation to FIG. 8. Mobile station 902 is a battery-powered
device so it also includes a battery interface 954 for receiving
one or more rechargeable batteries 956. Such a battery 956 provides
electrical power to most if not all electrical circuitry in mobile
station 902, and battery interface 954 provides for a mechanical
and electrical connection for it. The battery interface 954 is
coupled to a regulator (not shown) which provides power V+ to all
of the circuitry.
[0069] Mobile station 902 includes a microprocessor 938 (which is
one implementation of controller 806 of FIG. 8) which controls
overall operation of mobile station 902. Communication functions,
including at least data and voice communications, are performed
through communication subsystem 911. Techniques of the present
application are primarily performed through computer instructions
which microprocessor 938 (and/or DSP 920) executes. Microprocessor
938 also interacts with additional device subsystems such as a
display 922, a flash memory 924, a random access memory (RAM) 926,
auxiliary input/output (I/O) subsystems 928, a serial port 930, a
keyboard 932, a speaker 934, a microphone 936, a short-range
communications subsystem 940, and any other device subsystems
generally designated at 942. Some of the subsystems shown in FIG. 9
perform communication-related functions, whereas other subsystems
may provide "resident" or on-device functions. Notably, some
subsystems, such as keyboard 932 and display 922, for example, may
be used for both communication-related functions, such as entering
a text message for transmission over a communication network, and
device-resident functions such as a calculator or task list.
Operating system software used by microprocessor 938 is preferably
stored in a persistent store such as flash memory 924, which may
alternatively be a read-only memory (ROM) or similar storage
element (not shown). Those skilled in the art will appreciate that
the operating system, specific device applications, or parts
thereof, may be temporarily loaded into a volatile store such as
RAM 926.
[0070] Microprocessor 938, in addition to its operating system
functions, preferably enables execution of software applications on
mobile station 902. A predetermined set of applications which
control basic device operations, including at least data and voice
communication applications, will normally be installed on mobile
station 902 during its manufacture. A preferred application which
is loaded onto mobile station 902 may be a personal information
manager (PIM) application having the ability to organize and manage
data items relating to e-mail messages and voicemail messages, as
well as calendar data. Naturally, one or more memory stores are
available on mobile station 902 and SIM 952 to facilitate storage
of PIM data items and other information.
[0071] The PIM application preferably has the ability to send and
receive data items via the wireless network. In a preferred
embodiment, PIM data items are seamlessly integrated, synchronized,
and updated via the wireless network, with the mobile station
user's corresponding data items stored and/or associated with a
host computer system thereby creating a mirrored host computer on
mobile station 902 with respect to such items. This is especially
advantageous where the host computer system is the mobile station
user's office computer system. Additional applications may also be
loaded onto mobile station 902 through network, an auxiliary I/O
subsystem 928, serial port 930, short-range communications
subsystem 940, or any other suitable subsystem 942, and installed
by a user in RAM 926 or preferably a non-volatile store (not shown)
for execution by microprocessor 938.
[0072] In a data communication mode, a received signal such as a
text message (e.g. a short message service or SMS message), an
e-mail message, or web page download will be processed by
communication subsystem 911 and input to microprocessor 938.
Microprocessor 938 will preferably further process the signal for
output to display 922 or alternatively to auxiliary I/O device 928.
A user of mobile station 902 may also compose data items, such as
e-mail messages, for example, using keyboard 932 in conjunction
with display 922 and possibly auxiliary I/O device 928. Keyboard
932 is preferably a complete alphanumeric keyboard and/or
telephone-type keypad. These composed items may be transmitted over
a communication network through communication subsystem 911. For
voice communications, the overall operation of mobile station 902
is substantially similar, except that the received signals would be
output to speaker 934 and signals for transmission would be
generated by microphone 936. Alternative voice or audio I/O
subsystems, such as a voice message recording subsystem, may also
be implemented on mobile station 902. Although voice or audio
signal-output is preferably accomplished primarily through speaker
934, display 922 may also be used to provide an indication of the
identity of a calling party, duration of a voice call, or other
voice call related information, as some examples.
[0073] Serial port 930 in FIG. 9 is normally implemented in a
personal digital assistant (PDA)-type communication device for
which synchronization with a user's desktop computer is a
desirable, albeit optional, component. Serial port 930 enables a
user to set preferences through an external device or software
application and extends the capabilities of mobile station 902 by
providing for information or software downloads to mobile station
902 other than through a wireless communication network. The
alternate download path may, for example, be used to load an
encryption key onto mobile station 902 through a direct and thus
reliable and trusted connection to thereby provide secure device
communication.
[0074] Short-range communications subsystem 940 of FIG. 9 is an
additional optional component which provides for communication
between mobile station 902 and different systems or devices, which
need not necessarily be similar devices. For example, subsystem 940
may include an infrared device and associated circuits and
components, or a Bluetooth.TM. communication module to provide for
communication with similarly-enabled systems and devices.
Bluetooth.TM. is a registered trademark of Bluetooth SIG, Inc.
[0075] FIG. 10 is a block diagram illustration of pertinent
components of call control equipment 112 for use in the present
application. Call control equipment 112 of FIG. 10 includes a call
control server 1002 which has a wireless network interface 1004, an
IP network interface 1006, and a telephone landline network or
public branch exchange (PBX) interface 1008. Call control server
112 is the entity which contains the primary logic for control and
processing in accordance with the present application. The
functionality of call control server 1002 is implemented using
computer instructions stored in memory which are executed by one or
more processors (e.g. a microprocessor) within server 1002. This
functionality has been described previously in various embodiments
described in relation to FIGS. 1-5 and 7 above. IP network
interface 1006 of call control equipment 112 is used for
communication with the 802.11 wireless network through an IP
network (e.g. the Internet and/or Intranet), where conventional
VoIP communication protocols may be utilized. Wireless network
interface 1004 is used for communication with cellular network,
where conventional cellular network protocols (e.g. SS7 signalling
etc.) may be utilized for control and information communication.
Finally, PBX interface 1002 is used for facilitating incoming or
outgoing calls involving communication terminals over the landline
telephone network. Note that, depending on the specific
implementation, call control equipment 112 may only need only some
of these interfaces 1004, 1006, and 1008.
[0076] Thus, methods and apparatus for providing a seamless
switching of voice calls between different wireless networks have
been described. One illustrative method for use by a mobile device
of the present application includes the steps of maintaining voice
communications for a voice call with a communication terminal
through call control equipment, the voice call involving a traffic
channel established between a first wireless network and the mobile
device using a first transceiver portion which operates in
accordance with the first wireless network; causing a connecting
call to be established with the communication terminal through the
call control equipment based on identifying a predetermined
condition, the connecting call involving a traffic channel
established between a second wireless network and the mobile device
using a second transceiver portion which operates in accordance
with the second wireless network; and after the connecting call is
established, maintaining voice communications for the voice call
over the traffic channel established between the second wireless
network and the mobile device. In a preferred embodiment, one of
the first and the second wireless networks is operative in
accordance with a cellular telecommunications network and the other
one of the first and the second wireless networks is operative in
accordance with an 802.11 based wireless network. A computer
program product of the present application includes a storage
medium and computer instructions stored on the storage medium which
are executable by one or more processors of the mobile device for
performing the method as described. A mobile device of the present
application includes one or more processors and one or more
wireless transceivers coupled to the one or more processors, where
the one or more wireless transceivers include a first transceiver
portion operative in accordance with a first wireless network and a
second transceiver portion operative in accordance with a second
wireless network. The one or more processors of the mobile device
are operative to perform the method as described.
[0077] An illustrative method for use by call control equipment of
the present application includes the steps of facilitating an
establishment of a voice call between a mobile device and a
communication terminal through the call control equipment, the
voice call involving a traffic channel established between a first
wireless network and the mobile device; causing a connecting call
to be established between the call control equipment and the mobile
device during the voice call, the connecting call involving a
traffic channel established between a second wireless network and
the mobile device; and causing the connecting call to be connected
with the voice call so that voice communications for the voice call
are maintained over the traffic channel between the second wireless
network and the mobile device. In a preferred embodiment, one of
the first and the second. wireless networks is operative in
accordance with a cellular telecommunications network and the other
one of the first and the second wireless networks is operative in
accordance with an 802.11 based wireless network. A computer
program product of the present application includes a storage
medium and computer instructions stored on the storage medium which
are executable by one or more processors of the call control
equipment for performing the method as described. The call
controller server of the present application includes one or more
processors, memory coupled to the one or more processors, and
computer instructions stored in the memory, where the computer
instructions are executable by the one or more processors to
perform the method as described.
[0078] The above-described embodiments of the present application
are intended to be examples only. For example, one of the wireless
networks may operate in accordance with Wi-MAX technology, which is
based on the IEEE 802.16 Air Interface Standard for fixed wireless
broadband access systems employing a point-to-multipoint (PMP)
architecture. Those of skill in the art may effect alterations,
modifications and variations to the particular embodiments without
departing from the scope of the application.
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