Note: Descriptions are shown in the official language in which they were submitted.
CA 02444185 2007-12-20
1
METHOD OF INTELLIGENT ROAMING USING NETWORK
INFORMATION AND A WIRELESS COMMUNICATION DEVICE
BACKGROUND OF THE INVENTION
This is a divisional application of co-pending parent Canadian Patent
Application Serial No. 2,294,432 filed June 12, 1998.
Technical Field
This invention relates to wireless communications and, more particularly, to
the selection of a particular service provider in a multi service-provider
environment.
Description of the Related Prior Art
In a multi service-provider wireless communication environment, such as a
cellular network, multiple service providers may operate in a given geographic
area,
for example, a metropolitan area. Each service provider will have its own
"geographic network" in that area, and will be assigned a unique operational
"frequency" (which may comprise multiple frequencies, or a frequency band) for
that
geographic area. The service providers may have other geographic networks in
other
geographic areas. However, in those other geographic areas the service
providers
may be assigned different operational frequencies.
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In early versions of cellular phones, the subscriber's phone would be
pre-programmed so that on being turned on, i.e., "powered-up", the phone would
operate
at a pre-selected band, or would implement a pre-programmed search schedule to
find a
particular operating frequency band in accordance with the pre-programmed
schedule.
For example, the schedule might call for seeking service on a particular band
and, if no
service could be found on that band, the schedule might call for seeking
service from
non-preferred providers located on other bands. In later= devices the pre-
programmed
schedule in the phone could be manually altered by the user.
However, it should be recognized that in these early impleinentations the
number
of possible bands were few and there were only a small set of hailing
frequencies,
sometimes called "control frequencies". Accordingly, in implementing a search
schedule, all of the control channels could be scanned iri a relative short
period of time.
However, as many more frequencies became available, many more control channels
would have to be scanned to implement search schedules. This is a time
consuming
process, and consumers will not tolerate the associated delay on power-up.
To address this intensified problem of searching rapidly for available
appropriate
frequencies, more efficient search protocols were devised to enable the
subscriber's
phone to search, efficiently and rapidly, through the various available
operational
frequencies for one assigned to the subscriber's service provider, or, in the
absence of its
service provider in the specific geographic area, for one assigned to a
service provider
with whom the subscriber's service provider had a "partnering" arrangement.
(Such
protocols usually have to be implemented whenever the phone is powered-up,
even when
in its home area, because the phone does not know that iit is in its home area
until it has
found a channel that is broadcasting its home area identities. However, since
the purpose
of such search protocols is to enable rnore effective roarning operation, the
protocols are
called "roaming" schedules, even though they are most often implemented in the
subscriber's home area, where the subscriber is not tech;nically "roaming". It
should be
CA 02444185 2007-12-20
3
noted that with the ability to "roam" i.e., operate outside one's home area,
the
"wireless network" is broadened to include all networks on which the
subscriber may
get service).
FIG. 1 illustrates a portion of the radio frequency spectrum used today in
such
wireless communications. Frequency range 10, centered around 800 MHz, has
historically been known as the cellular frequency range. Frequency range 12,
centered about 1900 MHz, is a more recently established frequency range
associated
with personal communication services (PCS). Each range of frequencies, i.e.,
the
cellular and PCS, are broken into two portions; an uplink portion, that is
used for
communications from a mobile communication device to a base station such as a
cellular base station, and a downlink portion, that is used for communications
from
the base station to a mobile communication device. In cellular frequency range
10,
the uplink portion is labeled 14, and the downlink portion is labeled 16. In
the PCS
frequency range 12, the uplink portion is labeled 18 and the downlink portion
is
labeled 20.
Each of the frequency ranges is broken into bands which are typically
associated with different service providers. In the case of cellular frequency
range 10,
frequency bands 30 and 32 are designated band "a" for uplink and downlink
communications, respectively. In a particular geographic area, a cellular
service
provider is assigned frequency band "a" for use in mobile communications.
Likewise,
in the same geographic area another cellular service provider is assigned
frequency
bands 34 (uplink) and 36 (downlink) which are designated band "b". The
frequency
ranges assigned to the two service providers are sufficiently separated so as
to not
interfere with each other, thereby enabling the two separate service providers
to offer
service in the same geographic area.
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Recently, the US Government auctioned the PCS frequency spectrum to service
providers. As with the cellular frequency range, the PCS frequency range is
broken into
several bands with different service providers licensed to use different
frequency bands
within a particular geographical area. The PCS bands are referred to as A, B,
C, D, E and
F. The A band includes uplink band 50 and downlink band 52. The B band
includes
uplink band 54 and downlink band 56, Band C includes uplink band 58 and
downlink
band 60. Each uplink and downlink band of the A, B and C bands is
approximately 30
MHz wide. The D band includes uplink band 62 and downlink band 64. The E band
includes uplink band 66 and downlink band 68. Likewise, band F includes uplink
band
70 and downlink band 72. The uplink and downlink bands of bands D, E and F are
approximately 10 MHz wide each. It should be noted that in the combined
cellular and
PCS frequency bands, it is possible to have as many as eight different
wireless
communication service providers in a particular area.
Each of the different cellular and PCS bands corisist of control channels and
communication channels in both the uplink and downlink direction. In the case
of analog
cellular bands, there are 21 control channels for both the "a" and "b" bands.
Each of the
control channels include an uplink and a downlink portiion. The control
channels transmit
information such as a SOC (System Operator Code), a SID (System Identifier
Code),
paging information, call setup information, and other overhead information,
such as
information relating to registering with the mobile communication system. The
portion
of the cellular band's spectrum not occupied by the control channels is used
for
communication channels. Communication channels carry, for example, voice or
data
communications. As noted above, each channel consists of an uplink and
downlink
communications link.
Presently there are several cellular communication standards. An analog
standard
known as EIA/TIA 553 was built upon the AMPS (Advanced Mobile Phone Service)
standard. This standard supports 21 analog control channels (ACC) and several
hundred
CA 02444185 2003-10-22
J
analog voice or traffic channels (AVC). A newer standard is the EIA/TIA IS54B
standard which supports dual mode operation. Dual mode operation refers to
having an
analog control channel, and either an analog voice/traffic channel or a
digital voice/traffic
channel (DTC). The AVC or DTC are used for actual communications, and the ACC
is
used to transfer information relating to, for example, cal.l set-ups, service
provider
identification, and the other overhead or system information.
A newer standard, the EIA/TIA IS13b standard supports communications covered
by both analog and dual mode cellular, and also includes a totally digital
communication
scheme which was designed for the PCS frequency bands A-F and cellular
frequency
bands "a" and "b". This standard allows for a digital traffic channel (DTC)
and a digital
control channel (DCCH). In the case of the DTC, not only is the voice or data
communicated, but in addition, a digital channel locator (DL) is transmitted
in the DTC.
The DL enables a mobile communication device that locks onto the DTC to use
the
information in the DL to locate a DCCH for purposes of obtaining information
such as
the SOC, SID, paging information, or other system overhead information carried
on the
digital control channel.
When a mobile commun'rcat ron device such as a mobile telephone attempts to
register with the service provider, it locks onto a control. channel and reads
information
such as the SOC and SID. If the SOC and/or SID correspond to a service
provider with
which the user has a communication services agreement, the telephone may
register with
the service provider's mobile communication system via the uplink control
channel.
FIG. 2 illustrates different service-provider assignments in different parts
of the
United States. The Figure is a map of the United States illustrating
assignments in cities
such as Seattle, Chicago and Washington, DC. In Seattlle, for example,
frequency band A
has been licensed to SOC (Service Operator Code) 001 with a SID of 43 and band
C has
been licensed to SOC 003 with a SID of 37. In Chicago, suppose that frequency
band C
has been licensed to SOC 001 with a SID of 57, and that band B has been
licensed to
CA 02444185 2003-10-22
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SOC 003 with a SID of 51. In Washington, DC suppose that frequency band "a"
has
been licensed to a SOC 001 with a SID of 21, and that band A has been licensed
to
SOC 003 with a SID of 17. It should be noted that the same SOC may be found in
several different locations although on different frequency bands. It should
also be noted
that the same SOC will be associated with different SIDs in each geographical
area and
that in the same geographic area different service proviciers have different
SIDs. If a
particular subscriber to a wireless telecommunication service has an agreement
with a
service provider having a SOC of 001, that subscriber would prefer to use
systems with a
SOC of 001 because the subscriber is likely to receive a less expensive rate.
When the
subscriber is in Seattle he/she would prefer to be on band A, and if in
Chicago on band C,
and if in Washington, DC on band "a".
The above described situation presents a problem for a wireless communication
service subscriber. As a subscriber moves from one area of the country to
another, the
telephone, when turned on, searches for the "home" service provider, or a
service
provider with which the subscriber has a pre-arranged agreement, if, for
exarnple, the
subscriber travels from Seattle to Chicago, then when the phone is turned on
for the first
time in Chicago, the phone will search through the different bands of the
spectrum to
identify the service operator with the code 001 in order to find the desired
service
provider.
In order to find a particular service provider, the phone may have to search
through both the "a" and "b" cellular bands, and through the six PCS bands. It
should be
recalled that there are up to 21 different ACCs in each of the "a" and "b"
cellular bands.
It may be necessary to check 42 ACCs in order to find an ACC from which a SOC
or SID
may be obtained. Additionally, searching for a particular SOC or SID in PCS
bands A
through F is particularly time consuming, because, within a particular PCS
band, the
digital control channels (DCCHs), which contain the SOC and SID, are not
assigned to
specific frequencies. As a result, the mobile communication device may find it
necessary
CA 02444185 2007-12-20
7
to search through the spectrum of each PCS band looking for a DCCH, or an
active
DTC that has a digital channel locator (DL) which will direct the mobile
communication device to the DCCH. Accordingly, the process of searching for a
particular service provider is laborious and may require a period of time on
the order
of several minutes.
In the related applications cited above there are disclosed intelligent
roaming
techniques in which a particular search schedule is used to optimize the
search for a
preferred service provider. In some of the disclosed intelligent roaming
techniques,
the improved roaming search "schedule may be reprogrammed using signals
received
over the wireless communication channel" or based on "the prior history of the
mobile communication device's use". Additionally, as disclosed in U.S. Patent
No. 6,411,807 issued June 25, 2002 entitled "Roaming Authorization System", a
subscriber defined profile may be stored at the Home Location Register.
Roaming
authorization is then only granted consistent with permitted roaming time-
windows in
that profile.
SUMMARY OF INVENTION
The invention relates to how a subscriber's cellular phone selects, and
"registers onto", a particular range of operating frequencies (or "frequency
band"),
such as, for example, the frequency band assigned to the subscriber's selected
service
provider, in the geographic area in which the subscriber's cellular phone
happens to
be located and operating. (In this patent, the term "cellular phone" refers to
a
wireless, mobile phone that operates in a multi service-provider environment,
usually
a cellular environment. The term "registers onto" includes not only the
processes
involved in establishing a call, but also includes any communication between
the
network and wireless communication device, such as, for example, when the
device is
in standby mode. In particular, these "registrations" may give the network
information, for example, on the location of the device).
CA 02444185 2007-12-20
7a
This invention involves "intelligent roaming" - improved techniques for
subscriber selection of an optimum service provider when the subscriber's
phone is
powered-up, whether in the subscriber's home area or while roaming.
This invention is an improved intelligent roaming technique in which
information gathered by the wireless network is used to formulate an optimal
search
schedule. The invention contemplates the use of the types of information that
are
currently gathered by the network to design optimal intelligent roaming search
schedules. Of course, additional information, that the network may be designed
to
gather in the future, may also be used in the practice of this invention.
Based on the
invention an optimum search schedule can be "adaptively" predicted based on
information gathered by the network.
In accordance with one aspect of this invention, the information that may be
used to design intelligent roaming search schedules may be related to the
usage
history of the particular subscriber. For example, the network will know that
when the
particular subscriber is near the local airport the next location for that
particular subscriber is
CA 02444185 2003-10-22
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usually a specific distant city to which the subscriber, in fact, often flies.
A search
schedule that takes into account the frequency assignments of service
providers in the
specific distant city will then be used.
In accordance with another aspect of this invention, the information that may
be
used to design intelligent roaming search schedules may be related not only to
the usage
history of the pat-ticular subscriber but to the usage history of other
subscribers as well.
For example, the network will know that subscribers on a particular interstate
highway,
when reaching a service boundary, will most often make their next call from
the adjacent
service area. A search schedule that takes into account the frequency
assignment of
service providers in the adjoining areas will then be used. Similarly, in
other
embodiments of the invention, information related to the usage history of
subsets of
subscribers may be used to design efficient search schedules. In these and
other
embodiments of the invention, inforrnation gathered by the netwock permits
more rapid
selection of an optimum service-provider in a multi service-provider
environment.
Access to the network for this process not only provides information that is
not usually
available to the subscriber for designing search schedules, but, additionally,
may help
overcome storage and processing limitations of mobile communication devices.
The invention will be better understood, by recognizing that the information
that
is used to design the search schedule for a specific subscriber generally
falls into two
broad classes. First there is information related to the subscriber's last
registration on the
system. This information includes subscriber location as well as information
related to
the specific provider used during the last registration and the services
sought. A second
class of information relates to projecting where the subscriber will be at the
next
power-up. This information relates to past practices of the specific
subscriber, as well as
past practices of other subscribers or subsets of subscribers. This
"projection"
information can be analyzed based on many variables, such as last location of
the
CA 02444185 2009-01-14
9
subscriber, last call made by the subscriber, time of day and year, recent
movement of
the subscriber, historical practices of the specific subscriber, etc.
Although in the broad practice of this invention the search schedule is
designed based on information gathered in the network, the schedule itself
need not be
designed in the network. Accordingly, in some embodiments of the invention,
the
search schedule may be designed in the subscriber phone, but based on the
network
information. Of course, in other embodiments, the search schedule may be
designed
in a network element, or in a non-network element removed from the phone, and
transferred to the phone over-the-air, or otherwise. In either event, the
network
information, or the specific search schedule may be transferred to the mobile
phone
either over-the-air or manually.
In view of the limited memory available in the phone, the search schedule may
be updated periodically depending on the projected location of the phone.
Accordingly, for example, certain bands may be removed from the search
schedule
based on the projected location of the phone. Alternatively, the user may
indicate to
the network the location of the phone, and based on the network information
related
to that new location, a search schedule customized for that location may be
used.
Certain exemplary embodiments may provide a method for a communication
device to locate a wireless service provider in a multi service-provider
environment,
the communication device having a stored search schedule associated with a
plurality
of frequencies, the method comprising: predicting a future location of the
communication device based on information about the communication device's
registration on a network; generating the search schedule based on the future
location;
determining whether a last frequency used by the communication device has an
optimal service provider; and if the last frequency does not have an optimal
service
provider, examining one of the stored frequencies until a frequency is located
having
an acceptable service provider.
CA 02444185 2009-01-14
9a
Certain other exemplary embodiments may provide a wireless communication
device that locates a wireless service provider in a multi service-provider
environment,
comprising: a memory that stores frequencies, the stored frequencies
determined by a
future location, wherein the future location is predicted based on information
about the
communication device's registration on a network; and a processor that
determines
whether a last frequency used by the communication device has an optimal
service
provider, and if the last frequency used does not have an optimal service
provider,
examines one of the stored frequencies until a frequency is located having an
acceptable
service provider.
CA 02444185 2007-12-20
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention taken in conjunction with the invention described in
co-pending Canadian Patent Application Serial No. 2,294,432, filed June 12,
1998,
will be described in detail hereinbelow with the aid of the accompanying
drawings, in
5 which:
FIG. 1 illustrates the frequency spectrum used for wireless communications;
FIG. 2 illustrates service areas within the United States;
FIG. 3 illustrates a telecommunications system including wireless and wired
networks;
10 FIG. 4 is a block diagram of a mobile communication device;
FIG. 5 illustrates a search schedule;
FIG. 6 illustrates a search schedule ordered by registration history;
FIG. 7 illustrates a prioritized list of service providers;
FIG. 8 illustrates display of an alphanumeric tag on a mobile communication
device;
FIG. 9 is a flow chart illustrating a spectrum search routine;
FIG. 10 is a flow chart illustrating the global spectrum search routine;
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11
FIG. I 1 is a flow chart illustrating a periodic search routine; and
FIG. 12 is a flow chart illustrating a received signal search routine.
DETAILED DESCRIPTION
In describing the invention, we first describe the general characteristics of
a
wireless network, then we review the roaming concepts, and finally we discuss
embodiments specific to this invention.
General Characteristics of a Wireless Network
A Wireless Geographic Communications Network, 80, such as a Public Cellular
Network, that services a specific geographic area, is illustrated in FIG. 3.
The
Nationwide Wireless Network comprises a multitude of such Wireless Geographic
Communications Networks. The current Nationwide Wireless Network also
comprises
some form of Data Message Handler Network, connected to the Wireless
Geographic
Networks, to handle data related to calls made on the Nationwide Network. An
advanced
form of such a Data Message Handler Network, 102, is a[so shown in FIG. 3.
(The term
"wireless network" as used in this patent refers to the aggregation of
networks that may
have information useful in designing a search schedule for a particular mobile
device).
The Wireless Geographic Network generally comprises a plurality of Mobile
Switching Centers (MSC), 82, (also known as Mobile Telephone Switching Offices
(MTSO)) that are connected to one another. MSC, 82, is in communication with,
and
operates to process calls (e.g., switching, handing off, terminating,
originating, signaling,
etc.) involving, at least one mobile station or device, 84. The mobi(e
station, 84, may be
a conventional mobile cellular telephone or another type of wireless
communication
device.
CA 02444185 2003-10-22
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A wired communications network, 86, such as the Public Switched Telephone
Network (PSTN), generally comprises a plurality of conventional switches that
are
interconnected to enable originating station, 88, from which a call is placed,
to
communicate with other stations within or outside PSTN, 86. The originating
station, 88,
illustrated in FIG. 3, may be a conventional telephone or any other
communication device
connected to PSTN, 86.
Although the wireless telecommunications network, 80, need not be limited to
cellular networks, conventional cellular technology may be utilized to allow
the same
frequencies of a common allocated radio bandwidth to be reused in separated
local areas
or cells of a broader region. Each cell is served by a base transceiver
station, 90, which
communicates with a plurality of local transceivers, 84, one of which is
shown. The base
stations, 90, are interconnected via MSCs, 82, which are also connected to
PSTN, 86,
either individually, or through another MSC, as shown in FIG. 3. The base
station, 90,
and mobile stations, 84, communicate via radio connections. The base station,
90, may
be connected to an MSC, 82, via trunks that comprise, for example, wires,
radio links or
optical fiber, to carry the voice, or other data, and control messages,
between mobile
station, 84, and MSC, 82. As illustrated in FIG. 3, MSC, 82, is also connected
to PSTN,
86, to allow wireless stations, 84, of wireless network, 80, to communicate
with wired
stations of PSTN, 86, such as telephone, 88. While not illustrated, MSC, 82,
may also be
connected to integrated services digital networks (ISDN) for communicating
according to
the protocols of ISDN.
The wireless telecommunication network, 80, typically comprises many units
that
need to communicate signaling information for controlling connections, which
signaling
information may relate to call establishment, re-establishment (hand off),
dis-establishment (tear down) and maintenance (power control and other
processes).
Such signaling information is typically communicated over chaiunels separate
from the
channels carrying actual voice or data communications between the customers
being
CA 02444185 2003-10-22
1J
connected. Among the units that need to communicate are the mobile station,
84, the
base station, 90, connected by radio to the mobile station, 84, MSC, 82, and
the various
databases that are consulted for the establishment, maintenance and control of
mobile
calls, including the home location register (HLR), 96, and the visitor
location register
(VLR), 94, which are accessed through a conventional signal transfer point
(STP), 92.
The home location register (HLR) contains data for a mobile customer. The data
stored in the HLR is the permanent data that is independent of the customer's
present
location, plus temporary data such as location-related data and the addresses
of Service
Centers that have stored short messages for a mobile station. These addresses
are erased
after the short messages have been delivered. The HLR also indicates the
Signaling
System 7 (SS7) point code or other address for the network element that
contains the
VLR currently associated with the mobile station. The VLR contains current
data for
each mobile customer, including that customer's mobile station's present or
most recently
known area, the station's on/off status, and security parameters.
The components mentioned above may all cornrnunicate with a Data Message
Handler Network (DMH), 102, which collects information to form activity
records for the
network. These records include information related to every call made on the
wireless
network. The information in these records may include identification of the
subscriber,
the calling party, and the called party; the subscriber location at time of
the call; the date,
time and duration of the call, detailed information related to hand-offs, etc.
This
information is routed by the DMH Router, 106, to, for example, a billing unit,
107, that
creates the subscriber bills, and to a fraud detection unit, 104, that
analyzes usage patterns
to detect fraud. As discussed further below, in one aspect of the invention,
this
information is also used by an Intelligent Roaming Network Intelligence Unit
(IRNI),
105. The IRNI unit may obtain information from the fraud unit or may obtain it
directly
from the activity records database. This information may then be transmitted
to the
subscriber's mobile device, either with or without further processing, to be
used, in
CA 02444185 2003-10-22
14
accordance with this invention, to optimize the process by which the
transceiver selects a
service-provider in a multi service-provider environment.
Each mobile is typically assigned a"home" network. Accordingly, at any given
time, a particular mobile may be located either in its home network or
"roaming" in a
"visiting" network. The visiting network detects the presence of roaming
mobiles and
informs their home networks of the location of the roaming mobiles. The home
network
is responsible for communicating to the visiting network signaling
information,
including, for example, permissions to grant communication privileges to the
roaming
mobiles and a list of features to which the roaming mobiles subscribe.
FIG. 4 illustrates a block diagram of a mobile communication device such as a
cellular telephone or personal communication device. Mobile communication
device,
100, includes transceiver, 102, which sends and receives signals from antenna,
104.
Mobile communication device, 100, is controlled by control system, 106, which
may
include a microprocessor or a microcomputer. Control system, 106, uses memory,
108,
for storing programs that are executed and for storing iriformation that is
entered by the
user, the distributor, the communication services provider or the
manufacturer.
Information such as user preferences, user telephone numbers, preferred
service provider
lists and frequency search schedules are stored in memory, 108. Memory, 108,
may
include storage devices such as random access memory (RAM), read only memory
(ROM) and/or programmable read only memory (PROTvI). A user commLUlicates with
control system, 106, via keypad, I 10. Control system, 106, communicates
information to
the user via display, 114. Display, 114, may be used to display information
such as status
information and items such as telephone numbers entered via keypad, 110. Audio
information to be transmitted from the mobile communication device, 100, is
received via
microphone, 112, and audio communications received by mobile communication
device,
100, are played to the user via speaker, 116.
CA 02444185 2003-10-22
Intelli2ent Roaming Techniques
After initially powering-up, a mobile communication device locates a service
provider and registers with the service provider. The registration process
allows the
identity of a mobiie and its location to be given to its home network so that
the home
5 network can deliver, and bill for, calls initiated, or to be received, by
the mobile, whether
the mobile is in its home region or roaming.
As part of the registration process, a service provider must be selected.
Recalling
FIG. I service providers are located at a plurality of frequency bands across
the radio
spectrum. In order to find a service provider, the communication device
searches the
10 spectrum to identify available service providers. The communications device
examines
received service provider codes e.g., SOCs (Service Operator Codes) and/or
SIDs
(System ldentification Codes) to determine whether available service providers
are
optimal, preferred or prohibited service providers.
FIG. 9 illustrates a process or program that control system 106 may execute im
15 order to find a desirable service provider. After power-up, step 30 is
executed to
initialize a non-optimal flag by clearing the flag. Step 32 determines whether
the last
service provider, that is, the service provider used before the last power
down, was an
optimal service provider. This is determined by checking the SOC and/or SID of
the last
service provider and determining whether that service provider's SOC or SID
corresponds to the SOC or SID of an optimal service provider. The SOC or SID
of the
last service provider and a list of optimal and preferred service providers is
stored in
memory 16. If in step 32 it is determined that the prior service provider was
not optimal,
a global spectrum search is executed. If the last service provider was
optional, step 34 is
executed where system 104 attempts to lock onto the control signal of the
service
provider. If the lock is unsuccessful, which may indicate that that control
channel is no
longer available or out of range, the global spectrum search is executed. If a
lock is
successful, step 36 is executed. In step 36, it is determined whether the
control channel
CA 02444185 2003-10-22
16
contains the SOC or SID of an optimal service provider. Once again, this is
determined
by comparing the SOC or SID from the control signal with a list of optimal
service
provider SOCs or SIDs. If the SOC or SID does not belong to that of an optimal
service
provider, the global spectrum search 33 is executed and the identity of the
frequency
band in which the non-optimal SOC or SID was located is passed to global
search routine
33 so as to avoid unnecessarily searching this portion of'the spectrum again.
If in step 36
it is determined that an optimal service provider has been located, step 38
registers
communication device 100 with the service provider.
In FIG. 9, step 40 is an idle state where control system 106 simply monitors
the
control channel of the service provider for communication system overhead
information
and for paging information which may indicate an incotning communication.
While in
idle state 40, a timer is activated which permits a low-duty cycle search to
be performed
if the phone is presently registered in a non-optimal service provider system.
This
situation may arise if global spectral search 33 provides a preferred but not
optimal
service provider. Periodically, such as every 5 minutesõ step 42 is executed
to determine
whether the non-optimal flag has been set, if the non-optimal flag is not set,
control
system 106 returns to idle step 40. If the non-optimal flag has been set, step
42 leads to
the execution of periodic search routine 44, where a search is conducted in
order to
attempt to locate an optimal service provider. If periodic search routine 44
produces an
optimal service provider, the non-optimal service provider flag is cleared and
the mobile
communication device registers with the optimal service provider. The mobile
communications device then enters an idle state by executing step 40. If an
optimal
service provider is not located in routine 44, control system 106 returns to
an idle state by
executing step 40.
FIG. 10 illustrates a flowchart of global spectrum search routine 33 which is
executed by control system 106. At step 60 it is determined whether the last
control
channel used by the mobile communication device was a personal communication
CA 02444185 2003-10-22
17
services related control channel, that is, a control channel in the bands A
through F, If
the last control channel was not a PCS control channel, step 62 is executed.
In step 62 it
is determined whether the mobile communication device can lock onto, or
receive and
decode the last ACC (Analog Control Channel) that was used. If the mobile
communication device can successfully look onto the last ACC, step 64 is
executed. If
the communication device cannot lock onto the last ACC, step 66 is executed.
In step 66,
an RSS (Received Signal Strength Scan) is performed. This step involves the
mobile
communication device tuning to each of the 21 ACCs associated with the
cellular band of
the last used ACC, and attempting to lock onto the strongest received signal.
In step 68,
it is determined whether a lock has been achieved. In step 68 if a lock is not
obtained, a
predetermined search schedule is executed in order to find a service provider.
If in step
72 a lock is obtained, step 64 is executed where the SOC or SID obtained from
the
control channel is compared to a list of optimal SOCs or SIDs. In step 70, if
the received
SOC or STD is associated with an optimal service provider, step 72 is executed
where the
mobile communication device clears the non-optimal flag, registers with the
communication service provider, and then enters an idle state by executing
step 40 of
FIG. 9. If, in step 70 it is determined that an optimal service provider SOC
or SID was
not received, step 74 is executed, where the identity of the frequency band
just searched
is stored in memory 16.
Step 78 is executed after step 74, after 69 if a lock is not obtained, or
after step 60
if the last control signal was from a PCS frequency band. In step 78, a search
schedule is
downloaded using a master search schedule. When downloading the search
schedule in
step 78, frequency bands previously searched are removed frorn the downloaded
schedule
so as to avoid searching bands that have already been searched. For example,
bands
searched in the search routine discussed with regard to FIG. 9, and the
cellular band
search discussed with regard to step 74, are removed from the search schedule.
CA 02444185 2003-10-22
18
After the moditied search schedule has been loaded, a search pointer is
initialized
to point to the first band identified by the modified search schedule. The
first band
identified on the modified schedule is searched with regard to received signal
strength
(RSS) in step 79's RES routine. In the case of bands "a" and "b", the ACC with
the
strongest signal is selected. In the case of the PCS bands, that is the bands
A through F,
2.55 MHz sections of each band are searched in 30 kilohertz steps. The mobile
communication device tunes to the strongest signal that crosses a minimum
threshold,
e.g., -110 dBm, within the 2.5 MHz band being examined. In step 80 it is
determined
whether the signal is valid, that is, conforms to one of the above mentioned
standards. If
it is not valid, the search pointer is incremented in step 96, and if the
signal is valid,
step 82 is executed.
In step 82 it is determined whether the signal is an ACC. If the signal is an
ACC,
the SOC or SID is decoded in step 90. If the signal is not an ACC, step 84
determines
whether the received signal is a digital traffic channel (DTC) or a digital
control channel
(DCCH). If the signal is a DCCH the SOC or STD is extracted in step 90. If it
is
determined that the received signal is a DTC, step 86 is executed where the DL
(digital
channel locator) is extracted in step 88, the mobile communication device
tunes to the
strongest DCCH of the digital control channels identified by the DL. ln step
90, the SOC
or SID of the received DCCH is extracted and in step 91, it is determined
whether the
SOC or SID is associated with an optimal service provider. If the SOC or SID
is
associated with an optimal service provider, step 92 clears the non-optimal
flag and
step 96 registers the mobile communication device with the sei-vice provider.
After
step 96, the communication device enters the idle state in step 40 of FIG. 4.
If in step 92 it is determined that the SOC or SID does not belong to that of
an
optimal service provider, step 94 is executed, where the SOC or SID is stored
in memory
16 indicating whether the SOC or SID was at least a preferred, rather than an
undesirable
or prohibited, service provider with the spectral location of the SOCs or SIDs
control
CA 02444185 2003-10-22
19
channel. In step 96 the search pointer that identifies the band being searched
is advanced
to identify the next band in the schedule for searching.
In step 98 it is deterinined whether the pointer has reached the end of the
search
schedule. If the end of the search schedule has not been reached, step 82 is
executed to
perform another received signal strength search routine as discussed above,
and if the last
frequency band has been searched, step 100 is executed. ln step 100 the mobile
communication device registers with the best stored SOC or SID, that is, a SOC
or SID
that has at least been associated with a preferred service provider. The best
service
provider can be identified by comparing the stored SOCs or SIDs with a list of
preferred
SOCs or SIDs. The list of preferred SOCs or SIDs, can include the optimal
SOC(s) or
SID(s) and a prioritized list of preferred SOCs or SIDs where the higher
priority will get
preference for registration. The listing also includes undesirable or
prohibited SOC(s) or
SID(s) that are used only in emergencies (e.g., 911 calls) or if the user
enters an override
command. After registering with the service provider in step 100, step 102 is
executed to
set the non-optimal flag, and then step 40 of FIG. 9 is executed where the
mobile
communication device enters the idle state.
It should be noted that the searching operation of FIGS. 9 and 10 may be
carried
out in a simplified manner. With regard to FIG. 9, control system 106 may
execute
step 33 after step 30 while always skipping steps 32, 34, 36 and 38. With
regard to
FIG. 10, control system 106 may start the global spectrum search with step 78
while
always skipping steps 60-74.
FIG. 11 illustrates a flowchart for the periodic search routine executed by
control
system 106. In step 120, it is determined whether the periodic search flag has
been set.
If the periodic search flag has not been set, step 122 is executed. In step
122 the periodic
search flag is set and the search schedule is initialized by loading the
master search
schedule into the search schedule used by the periodic search routine;
however, the
frequency band currently being received is not included in the search schedule
used for
CA 02444185 2003-10-22
the periodic search routine. Step 122 also sets a search pointer to the first
band in the
search schedule.
In step 124 a received signal strength search (RSS) routine is conducted. As
in
step 79 of the global spectrum search routine of FIG. 10, step 124 is an RSS
routine of
5 any PCS and cellular bands that are in the search schedu.le, In the case of
a cellular band
search, the 21 ACCs are searched using a received signal strength search,
i.e., the
transceiver tunes to the strongest ACC. In the case of a PCS frequency band
search, as
discussed earlier, each band is broken into segments of approximately 2.5 MHz
where a
search of each segment is conducted in 30 kilohertz steps. The strongest
signal within the
10 2.5 MHz segment and above a minimum threshold, sucll as -110 dBrn, is
selected. In
step 126, the selected signal is examined to determine if it is valid by
conforming to one
of the previously referenced standards. If the signal is invalid, step 144 is
executed and if
the signal is valid, step 129 is executed. Step 129 determines whether the
signal is an
ACC. If the signal is an ACC, step 130 is executed where the SOC or SID is
extracted
15 and if the signal is not an ACC, step 132 is executed. Step 132 determines
whether a
DTC signal has been received. If the signal is not a DTC signal (therefore it
is a DCCH
signal), step 130 is executed to extract the SOC or SID from the DCCH signal.
If in step
132 it is determined that a DTC has been received, step 134 is executed to
extract the DL
to enable tuning to a DCCH. In step 136 a received signal strength search is
conducted of
20 the DCCHs where the strongest signal is selected, and then step 130 is
executed to extract
an SOC or SID from the signal.
In step 138 it is determined whether the SOC or SID is an optimal SOC or SID.
If
the SOC or SID is optimal, step 140 clears the non-optimal flag and in step
142 the
mobile communication device registers with the service provider associated
with the
optimal SOC or SID. Step 40 of FIG. 9 is then executed to enter the idle
state. If in
step 138 it is determined that the SOC or SID was not an optimal service
provider,
CA 02444185 2003-10-22
21
step 144 is executed. In step 144 the search pointer is incremented to the
next band to be
searched.
In step 146, it is determined whether the entire search schedule has been
completed. If the schedule has not been completed, step 40 is executed so that
the mobile
communication device can be returned to the idle state. If in step 146 it is
determined
that the search schedule has been completed, step 148 clears the periodic
search flag and
then step 40 is executed so that the mobile communication device can enter the
idle state.
FIG. 12 illustrates a flowchart of the RSS routine, or received signal
strength
search routine, which is carried out, for example, in steps 79 of FIG. 10 and
124 of
FIG. 11. Step 170 determines whether the band being searched is one of the "a"
or "b"
cellular bands. If a cellular band is being searched, step 172 is executed
where the 21
ACCs are searched to determine which is the strongest. Transceiver 12 tunes to
the
strongest ACC under the control of control system 106 and then the RSS routine
is
exited. If in step 170 it is determined that a cellular band is not being
searched, step 178
tunes transceiver 12 to the beginning of the first 2.5 MHz band in the PCS
band being
searched. Step 178 also clears a search scratch pad mernory location in memory
16. The
search scratch pad is used to record, the amplitude or str-ength and location
of a received
signal.
In step 180 it is determined whether the signal being received is greater than
a
threshold. If the signal is greater than the threshold, step 182 is executed,
if the signal is
not greater than the threshold, step 184 is executed. In step 182 it is
determined whether
the received signal strength is greater than the signal strength value stored
in the search
scratch pad. If the received signal is not greater then step 184 is executed.
If the received
signal strength is greater, step 186 is executed and the present signal
strength is recorded
in the search scratch pad with the received signal's location in the spectrum.
CA 02444185 2003-10-22
22
In step 184, transceiver 12 is tuned to a frequency 30 kilohertz higher than
the
frequency at which it was tuned. Step 188 determines whether the new frequency
extends beyond the 2.5 MHz band currently being searched. If the new frequency
does
not exceed the 2.5 MHz band, step 180 is executed to orice again examine the
received
signal strength relative to the signal strength or arnplitude value stored in
the search
scratch pad. If in step 188 it is determined that the 30 kilohertz increment
extends
beyond the 2.5 MHz band being examined, step 190 is executed.
In step 190, the transceiver tunes to the signal location specified in the
search
scratch pad. If the signal is a valid signal and can be decoded, the RSS
routine is exited.
If the signal is not valid or cannot be decoded, e.g., the signal does not
conform to the
above-referenced standards, step 192 is executed. In step 192, the transceiver
is tuned to
the beginning of the next 2.5 MHz band within the PCS band being searched.
Step 194
determines whether the new 2.5 MHz band extends beyond the PCS band currently
being
searched. If the new increment extends beyond the PCS band being searched, the
periodic search routine is exited. If the 2.5 MHz increase does not result in
extending
beyond the PCS band being searched, step 196 is executed. In step 196, the
search
scratch pad containing signal strength measurements and signal location
inforination is
cleared to prepare for searching another band. After step 196, step 180 is
executed as
described above.
FIG. 5 illustrates a master search schedule. The master schedule is used to
initialize search schedules used in the above described search routines. The
master
search schedule is stored in a memory such as memory 108. The master search
schedule
can be initially programmed by the mobile communication device's manufacturer,
distributor or user. It should be noted that the first location in the search
schedule may be
left unprogrammed. If left blank, the blank is ignored wlien initializing the
search
schedules for the search routines. It is desirable for the first location to
be programmed
with the band in which the user's home service provider resides. For example,
if the user
CA 02444185 2003-10-22
23
has a service agreement with a service provider who is licensed to operate in
PCS band B
within the SID or geographical area in which the user most frequently is
located, band B
is programmed into the first slot of the master search schedule. If, for
example, band B is
programmed in the first slot, the slot originally containirig band B is made
blank. This
avoids searching the same band twice.
The master search schedule may be reprogrammed using signals received over the
wireless communication channel. For example, the mobile communication device
may
be restricted to accepting new programming for the master search schedule only
from a
service provider transmitting the home SID and an optimal SOC, it is also
possible to
accept over the air programming if the service provider sends a prearranged
code. It is
desirable to restrict the over the air programming through the use of codes,
home SIDs
and/or optimal SOCs to avoid unintentional or undesirable altering of the
master search
schedule. Over the air programming may be implemented using for example,
logical
sub-channels of a digital control channel. The logical sub-channels have the
capability to
transmit data addressed to a particular mobile communication device and to
receive data,
such as confirmation data, fi=om the mobile communications device.
When the search schedules are initialized using the master search schedule, it
is
also possible to precede the first location in the master search schedule with
other
frequency bands based on, for example, the prior history of the mobile
communication
device's use. For example, the first location searched nzay be the location
where the
phone was last turned off (powered down) or the location where the phone was
last
turned on (powered-up). Such personal use information for the subscriber may
be stored
at the subscriber's HLR in the wireless telecommunications network.
Advantageously, the master search schedule may be reprogrammed by the
wireless telecommunications network with search schedules optimized for the
geographic
location in which the mobile communications device last registered. For
example, if a
New York based subscriber was roaming and registered in Chicago, the HLR for
the
CA 02444185 2007-12-20
24
subscriber would provide a search schedule to be downloaded to the mobile
communications device with search information particular to the midwest.
In one aspect of this invention, the frequency band search schedule may be
defined based upon supervision of the search process by the wireless
telecommunications
network. By this method, the wireless telecommunications network 80 may
provide,
develop, and maintain a table in HLR 96 for a counter associated with each
frequency
band in the master search schedule. For example, while roaming, each time the
mobile
communication device 100 acquires service from a preferred provider, the
counter value
associated with the frequency band is incremented thereby retaining
information
establishing a "personal roaming history" for the user. The wireless
telecommunications
network then downloads these counter values to the mobile communications
device to
alter the order of search of the frequency bands of the master search
schedule.
FIG. 6 illustrates a table stored in HLR 96 providing a counter associated
with
each frequency band in the master search schedule of FIG. 8. Based upon the
counter
values in the table, the frequency band with the highest registration success
rate as
defined by its associated counter value would follow the home frequency band
in the
master search schedule. Thereafter, each additional frequency band with a non-
zero
counter would follow, according to its counter value, from highest to lowest.
Frequency
bands with a counter value of zero would then follow non-zero entries in their
originally
defined order.
As preferably embodied, the counter associated with each frequency band should
store only a finite number of registrations, e.g., 10, to keep storage
requirements in
HLR 96 to a minimum. Additionally, the stored counter values may represent
time-weighted registrations with more weight given to the most recent
registrations.
Advantageously, such time weighting of the counter values will serve to
optimize search
efficiency.
CA 02444185 2007-12-20
It will be appreciated that the occasion may arise when the master search
schedule
needs to be reset and the order of search may be redefined and the counter
values zeroed
by any of the previously discussed programming methods.
FIG. 7 illustrates a table stored in HLR 96 defining the optimal service
provider's
5 SOC and SIDs, and preferred service provider's SOCs and SIDs. The SOC or SID
with
the lowest number has the highest priority and is preferred over service
providers with
higher numbers and therefore a lower priority. For example, an SOC or SID with
a
priority level 2 would be preferred over an SOC or SID with a priority level
of 5. The
table may also include SOCs or SIDs that are undesirable or prohibited. In the
case of
10 SOCs or SIDs that are prohibited, it is desirable to permit connection to
the prohibited
SOCs or SIDs when an emergency call, such as a 911 call, is attempted or when
the user
enters an override command. The table in FIG. 7 may be programmed by the
manufacturer, by the distributor when the phone is purchased or by the user.
It is also
possible to program the table of FIG. 7 over the air using restrictions
similar to those used
15 when programming the master search schedule over the air.
Multiple service provider categories may be identified by matching the SID or
SOC broadcast on a control channel with the entries in the table of FIG. 7.
These
categories may include:
(1) home - service provider of choice and normally the service provider with
20 whom the user has a service agreement. If a mobile communication device is
registered
on or finds a control channel for a home service provider, the device does not
attempt to
find service on any other frequency band.
(2) partner - a partner with the home service provider. If a mobile
communication device is registered on or finds a control channel for a partner
service
25 provider, the device does not attempt to find service on any other
frequency band.
CA 02444185 2007-12-20
26
(3) preferred - a service provider with whom the home service provider has a
preferential rate and/or service agreement. The mobile communication device
will
register with a favored service provider only if a home or partner service
provider is not
found. On the occurrence of certain events, such as a control channel change
and/or
periodically, the mobile communication device will search other frequency
bands for a
home or partner service provider.
(4) forbidden - a service provider which is never used under normal
circumstances.
(5) neutral - a service provider not identified by a SID or SOC entry in the
table of FIG. 7. The mobile communication device will register on a neutral
service
provider if none of home, partner, or preferred service providers are found.
On certain
events such as a control channel change and/or periodically, the mobile
communication
device will search other frequency bands for a home, partner, or preferred
service
provider.
In alternative embodiments of the invention, "alpha tags", which are stored in
HLR96, may be displayed on a mobile communication device identifying a
particular
service class while the mobile communication device is in idle or camping
mode. The
alpha tags can be programmed or changed as part of over-the-air activation or
over-the-air programming as previously discussed and stored in memory 108 of
the
mobile communications device. In an instance where XYZ is the home service
provider,
the alpha tags could be:
(1) home - "XYZ"
(2) partner - "XYZ partner"
(3) preferred - "XYZ preferred"
CA 02444185 2003-10-22
27
(4) neutral - "ROAMING'".
Existing standards allow for the broadcast of an alpha tag on a control
channel and
its display on a mobile communication device when in the idle or camping
state. For
instance, if a mobile communication device used by an XYZ subscriber was in an
ABC
market, the phone might display "ABC'". The system described herein, however,
would
allow the home service provider XYZ to control the mobile coinmunication
device to
display "XYZ" as illustrated in FIG. 8. Further, alpha tags could be updated
as marketing
requirements dictate.
Intelligõent Roaming Usina Network Gatliered Infornnation
One aspect of this invention is an improved intelligent roaming technique in
which information gatherecl by the wireless network is used to formulate an
optimal
search schedule, such as the exemplary Master Search Schedule identified in
FIG. 5. The
invention contemplates the design of optimal intelligent roaming search
schedules using
the types of information that are currently gathered by the network. However,
additional
information, that the network may be designed to gather in the future, may
also be used in
the practice of this invention.
The invention will be better understood, by recognizing that the information
that
is used to design the search schedule for a specific subscriber generally
falls into two
broad classes. First there is information related to the subscriber's last
registration on the
system. This information may include subscriber location as well as
information related
to the provider used during the last registration and the services sought. A
second class
of information relates to projecting where the subscriber will be at the next
power-up.
This information relates to past practices of the specific subscriber, as well
as past
practices of other subscribers or subsets of subscribers. This "projection"
information
can be analyzed based on many variables, such as last location of the
subscriber, last call
CA 02444185 2003-10-22
28
made by the subscriber, time of day and year, recent movement of the
subscriber,
historical practices of the specific subscriber, etc.
In accordance with one aspect of this invention, the information that may be
used
to design intelligent roaming search schedules may be related to the usage
history of the 5 particular subscriber. For example, information related to
previous registrations for the
particular subscriber will show that when the subscriber is near the local
airport the next
registration location for that particular subscriber is usually a specific
distant city.
Clearly, the network inforniation is reflecting the fact that the subscriber
often flies from
the local airport to the specific distant city. A search schedule that takes
into account the
frequency assignments of the subscriber's service providers in the specific
distant city
will then be used. Alternatively, the subscriber may fly to any one of a
number of distant cities and, in that situation, information reflecting the
frequency assignments of all those
service providers may be used in designing a search schedule.
The information that is most applicable to the design of a search schedule at
any
given time may be further narrowed by using additional information available
to the
network. For example, network information may show that on a holiday weekend
when
the subscriber is near the local airport, the subscriber's wireless
communication device
next tries to register at a particular resort location. The search schedule
can then take that
information into account, if the current tirne is that holiciay weekend. Under
such 20 circumstances, the optimum search schedule will first seek the
subscriber's preferred
service providers at the resort location.
In accordance with another aspect of this invention, the information that may
be
used to design intelligent roaming search schedules may be related not only to
the usage
history of the particular subscriber but to the usage history of other
subscribers as well.
For example, the network will know that subscribers on a particular interstate
highway,
when reaching the state boundary, will most often make their next call from
the adjacent
state. Clearly, the network information reflects the fact that this highway
crosses a state
CA 02444185 2003-10-22
29
boundary entering into another geographic network witli a different set of
communication
parameters, such as SOCs, SIDs, operating frequencies, and even available
service
providers. A search schedule that reflects the frequency assignment of service
providers
in the adjoining areas of the adjacent state will then be used. Similarly, in
other
embodiments of the invention, information related to the usage history of
subsets of
subscribers may be used to design efficient search scheclules.
In these and other ernbodiments of the invention, information gathered by the
network permits more rapid selection of an optimum set=vice-provider in a
multi
service-provider environment. Access to network information for the design of
intelligent roaming search schedules, in accordance witli this invention, not
only provides
information that is not usually available to the subscriber for designing
search schedules,
but, to the extent that such information results in more efficient search
schedules, helps
overcome storage and processing limitations of mobile communication devices
when
seeking an optimum service provider in a multi service-provider environment.
Although in the broad practice of this invention the search schedule is
designed
based on information gathered in the network, the schedule itself need not be
designed in
the network. Accordingly, in some embodiments of the invention, the search
schedule
may be designed in the subscriber phone, but based on the network information.
Of
course, in other embodiments, the search schedule may 'be designed in a
network element,
or in a non-network element removed fi-om the phone. The information and/or
the search
schedule may be transferred to the phone over-the-air or manually.
In some embodiments of the invention, the subscriber may provide information
that will help in the design of the search schedule. For example, the
subscriber can
indicate the location of the next power-up and the network can then select
with certainty
the information that would provide an optiinum search schedule for that power-
up, rather
than relying on information that only permits a statistical projection of the
location of the
next power-up. Likewise, once the communication device has registered in a new
CA 02444185 2003-10-22
location, search related information that is not useful, based on the new
location may be
removed froin the communication device to save memory and other resources.
In view of the limited memory available in the phone, the search schedule may
be
updated periodically depending on the projected location of the phone.
Accordingly, for
5 example, certain bands may be removed from the search schedule based on the
projected
location of the phone. Alternatively, the user may indicate to the network the
location of
the phone, and based on the network information related to that new location,
a search
schedule customized for that location may be used.
Many wireless networks are currently configured to gather information for
billing,
10 fraud prevention and other purposes. That information also relates to usage
and may be
useful in intelligent roaming. Accordingly, in an embocliment of the
invention, that
information is used to configure a search schedule.
In FIG. 3 there is an illustrative schematic of a Data Message Handler (DMH)
that
gathers information from various geographic networks that may be used in
iritelligent
15 roaming. As shown in the Figure a plurality of cellular networks may be
joined in a
cooperative North American Cellular Network (NACN) High Speed Data Network
(HSDN). Currently, the NACN establishes and abides by various standard
protocols and
procedures. As part of the NACN, for example, there may be an agreed upon
procedure
for gathering "Activity Records" reflecting information related to all
cellular calls. This
20 information may include, for each call, the identity and location of each
calling and called
pai-ty, the length of the call, the date and time of the call, cells traversed
during the call,
etc. As shown in the Figure, this information is used, for example, for
billing purposes,
and, when further analyzed, to detect fraud. This further analysis necessary
for detection
of fraud usually involves study of the mobility characteristics of the
subscriber and
25 comparing that analysis to historical patterns for that subscriber or to
reasonable
movement rates. So, for example, if a subscriber makes a call from New York at
one
CA 02444185 2003-10-22
31 -
moment, and then shortly thereafter makes a call from San Francisco, it is
likely that one
of the calls originated with a fraudulently cloned transceiver.
The very same information that may be gathered by the network in, for example,
the DMH, inay be used to configure a search schedule that is used during
registration to
select a service provider. Accordingly, in an illustrative embodiment of the
invention, an
Intelligent Roaming Network Intelligence Unit (IRNI) receives at least some of
the same
information that is used by the Fraud Detection Unit. In simpler embodiments
of the
invention this information is used to construct a search schedule that simply
searches first
for the SOC and SID that were used by the subscriber.
In one embodiment of the invention, the information used to design a search
schedule may include information relating to service providers preferred by
the
subscriber in particular geographic location on previous transmissions. The
search
schedule designed by the device or the network can theri look for such service
providers
on a priority basis when in the appropriate geographic location. Updated
information or
search schedules may be downloaded, manually or over-the-air, every time the
subscriber
powers-up or after a given number of power-ups.
In still other embodiments, the inventive method may be used when an already
powered-up phone is approaching another Wireless Geographic Network. In
accordance
with this embodiment, the phone is instructed to transfer to a SOC and SID of
a preferred
service provider in the new Wireless Geographic Netwark when the boundary is
crossed.
It will be appreciated that the invention takes advantage of the information
the
wireless telecommunications network maintains on subscriber locations, band
registrations, carriers, etc., to find an optimal frequency for a mobile
communications
device. In particular, when the mobile communications device is turned on, the
device
may switch to intelligent roaming procedures and register with the best
carrier available.
CA 02444185 2003-10-22
32
The wireless telecommunications network may tlien update the stored
information in the
mobile communications device to optimize future searches.
It will also be appreciated that the invention overcomes significant
limitations of
the mobile communications device in intelligent roaming applications. More
particularly,
such devices are restricted in the amount of inemory provided. Thus, optimized
search
schedules cannot be provided for all possible scenarios that the subscriber
may encounter.
The instant invention shifts the burden of maintaining the information to the
wireless
telecommunications network, and may involve downloading only the immediately
pertinent information, thereby permitting operation of the rnobile
communications device
with substantially less memory.
While the invention has been described in its preferred embodiments, it is to
be
understood that the words which have been used are words of description,
rather than
limitation, and that changes may be made within the purview of the appended
claims
without departing from the true scope and the spirit of the invention in its
broader
aspects.
