(12) United States Patent
`Bamburak et al.
`
`USOO6195532B1
`(10) Patent No.:
`US 6,195,532 B1
`(45) Date of Patent:
`*Feb. 27, 2001
`
`(54) METHOD FORCATEGORIZATION OF
`MULTIPLE PROVIDERS IN A WIRELESS
`COMMUNICATIONS SERVICE
`ENVIRONMENT
`(75) Inventors: Michael D. Bamburak, Columbia, MD
`(US); John J. Daly, Neshanic Station,
`NJ (US); Christopher Gregory
`Lawrence; Michael Edward Prise,
`both of Kirkland, WA (US); Michael
`Allen Raffel, Redmond, WA (US)
`
`(*) Notice:
`
`rr. A
`(73) ASSignee: STST Wireles Srcs. Inc., Redmond,
`(US)
`This patent issued on a continued pros
`ecution application filed under 37 CFR
`1.53(d), and is subject to the twenty year
`patent term provisions of 35 U.S.C.
`154(a)(2).
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`This patent is Subject to a terminal dis-
`laimer.
`CaC
`(21) Appl. No.: 08/672,908
`(22) Filed:
`Jun. 28, 1996
`7
`(51) Int. Cl." ................................ H04Q 7/00; H04Q 9/00
`(52) U.S. Cl. ........................ 455/31.1; 455/62; 455/1613;
`455/168.1; 455/185.1
`(58) Field of Search ........................... 455/62, 67.1, 67.7,
`455/120, 154.1, 1542, 160.1, 1611-168.1,
`179.1, 180.1, 186.1, 186.2, 185.1, 447,
`450, 464, 161.3, 161.2, 422, 551, 552,
`31.1
`
`(56)
`
`4,788,543
`
`References Cited
`U.S. PATENT DOCUMENTS
`11/1988 Rubin ................................... 455/527
`
`:
`
`2/1990 Hanawa.
`4.903,330
`4/1990 Blair ....................................... 379/59
`4,916,728
`SEC Shepp et al. .
`...
`arui .
`2- Y
`-2
`10/1992 Zicker .................................... 379/59
`5,159,625
`3. t1993 George.
`24
`Y-2
`f1994 Hurst et al. .
`5,404,355
`4/1995 Raith.
`2 - - -2
`
`(List continued on next page.)
`
`FOREIGN PATENT DOCUMENTS
`2115877
`11/1994 (CA).
`O 459 344 A1 12/1991 (EP).
`O 510322 A2 10/1992 (EP).
`O 78:
`12, 8. o HO4O/7/32
`OTHER PUBLICATIONS
`
`“System Selection for Preferred Roaming Stage 1 Descrip
`tion-Baselin Text”, Jun. 1996.
`
`Primary Examiner William A. Cuchlinski, Jr.
`ASSistant Examiner-Gertrude Arthur
`(57)
`ABSTRACT
`A communication device locates a preferable wireleSS Ser
`Vice provider in a multi-Service provider environment using
`a frequency band Search Schedule. Initially, the communi
`cations device registers with a leSS preferred Service pro
`vider in a first frequency band. While remaining registered
`with the less preferred Service provider, the device examines
`Several frequency bands in the order Specified by the fre
`quency band Search Schedule. A frequency band is examined
`by dividing the frequency band into many Sub-bands, and by
`locating the Strongest Signal above a threshold within the
`Sub-band being examined. The examination continues until
`a Second frequency band having a more preferred Service
`provider is located. The communication device then regis
`ters with the more preferred Service provider. The category
`of Service provider may be identified and displayed on the
`communication device.
`
`10 Claims, 6 Drawing Sheets
`
`10
`UPLINK/ } DOWNLINK/
`TRANSMIT
`RECEIVE
`14
`16
`als
`Ob
`so
`34 32?
`36
`800 MHz
`CELULAR
`
`g
`
`UPLINK/
`TRANSMIT
`18
`
`66
`
`58 R p s
`g :
`A || ||
`30
`30
`30 MOMOMO 30
`1900 MHz
`PCS
`
`DOWNLINK/
`RECEIVE
`20
`
`s
`
`30
`
`68
`
`?
`60
`C DEF
`30 OOO
`
`Dell Inc., Ex. 1026
`Page 1 of 14
`
`

`

`US 6,195,532 B1
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`4/1995 Burke et al..
`5,406,643
`36 9. NS set al
`2 : 1 - 2
`f
`odges et al. .
`5,442,806 * 8/1995 Barber et al..
`5,463,675 * 10/1995 Gerszberg.
`5,479,484
`12/1995 Mukerjee et al. .
`5,483,684 * 1/1996 Ono et al. ......................... 455/168.1
`5,504.803
`4/1996 Yamada et al. .
`5,509,052
`4/1996 Chia et al..
`5,513,242
`4/1996 Mukerjee et al..
`5,513.247
`4/1996 Murkerjee et al..
`5,517,677
`5/1996 Moon ................................ 455/161.1
`5,524,135
`6/1996 Mizikovsky et al..
`5,541,977
`7/1996 Hodges et al..
`
`5,586.338
`5,590,397
`5,603,084
`5,613.204
`5,613.208
`5,655,218
`5,711,001
`5,734,980
`5,754,542
`5,754,952
`5,761,618
`5,768,380
`5,790,952
`2 -- Y-2
`
`12/1996 Lynch et al..
`12/1996 Kojima.
`2/1997 Henry, Jr. et al..
`3/1997 Haberman et al..
`3/1997 Blackman et al..
`8/1997 Smolinske ............................ 455/435
`1/1998 Bussan et al. .
`3/1998 Hooper et al. .
`5/1998 Ault et al..
`5/1998 Hodges et al. .
`6/1998 Lynch et al..
`6/1998 Rosauer et al. .
`8/1998 SeaZholtz et all
`eaZOZ, e a
`
`* cited by examiner
`
`Dell Inc., Ex. 1026
`Page 2 of 14
`
`

`

`U.S. Patent
`
`Feb. 27, 2001
`
`Sheet 1 of 6
`
`US 6,195,532 B1
`
`10
`s
`UPLINK/ "DOWNLINK/
`Taut Rs."
`
`301
`
`34 32
`
`800 MHz
`CELLULAR
`
`
`
`
`
`
`
`
`
`A
`SEATTLE YSOC-001
`SIDE43
`
`C
`SOC-003
`SID=37
`
`FIG. 1
`
`UPLINK/
`TRANSMIT
`18
`
`12
`)
`
`DOWNLINK/
`RECEIVE
`20
`
`50
`S.
`
`54
`S.
`B
`
`58 te 52
`S. NY S S
`
`56
`S
`
`60 sta
`S NYS
`
`1900 MHz
`PCS
`
`
`
`A
`SOC-003
`STD-17
`
`FIG. 2
`
`C
`SOC-001
`CHICAGO t SID=57
`B
`SOC-003
`SID=51
`
`O
`R
`S25
`?
`
`Dell Inc., Ex. 1026
`Page 3 of 14
`
`

`

`U.S. Patent
`
`Feb. 27, 2001
`
`Sheet 2 of 6
`
`US 6,195,532 B1
`
`CONTROL
`SYSTEM
`
`18
`
`FIG. 4
`
`
`
`
`
`POWER UP
`
`CLEAR PERIODIC
`SEARCH FLAG
`CLEAR NON-OPT. FLAG
`
`
`
`30
`
`32
`
`34
`
`36
`
`
`
`33
`
`GLOBAL SPECTRUM
`SEARCH
`
`Dell Inc., Ex. 1026
`Page 4 of 14
`
`

`

`U.S. Patent
`
`Feb. 27, 2001
`
`Sheet 3 of 6
`
`US 6,195,532 B1
`
`FIC. 6
`
`78
`
`INITIALIZE SEARCH
`SCHEDULE AND
`SEARCH POINTER
`
`60
`
`YES
`
`
`
`
`
`RSS OF 21 ACCS OF
`LAST CELLULAR
`
`NON-OPT
`
`BEST STORED
`
`SET NON-OPT
`FLAG
`
`
`
`
`
`TO IDLE
`
`Dell Inc., Ex. 1026
`Page 5 of 14
`
`

`

`U.S. Patent
`
`Feb. 27, 2001
`
`Sheet 4 of 6
`
`US 6,195,532 B1
`
`FIG. 6
`
`
`
`
`
`122
`
`FLAG SET
`
`INITALIZE SEARCH
`SCHEDULE AND
`SET PERIODC
`SEARCH FLAG
`INITIALIZE PERIODIC
`SEARCH POINTER
`
`
`
`
`
`
`
`YES
`
`154
`
`CHECK DL
`
`SS DCCHS R
`
`
`136
`
`130
`
`140
`
`NON-OPT
`FLAG
`
`REGISTER
`142
`
`144
`
`INCREMENT SEARCH
`SCHEDULE
`POINTER
`
`
`
`146
`
`
`
`END OF SEARCH
`SCHEDULE 2
`
`148
`
`CLEAR PERIODIC
`SEARCH FLAG
`
`TO IDLE
`
`Dell Inc., Ex. 1026
`Page 6 of 14
`
`

`

`U.S. Patent
`
`Feb. 27, 2001
`
`Sheet 5 of 6
`
`US 6,195,532 B1
`
`172
`
`
`
`
`
`170
`
`
`
`
`
`
`
`
`
`
`
`
`
`RETURN
`
`FIG. 7
`
`178
`
`TUNE TO START OF FIRST
`2.5 MHZ BAND AND CLEAR
`SEARCH SCRATCH PAD
`180
`
`SIG > THRESHOLD
`
`182
`
`SIG > STORED NYES
`WALUE
`
`186
`
`STORE SIG
`STRENGTH AND
`LOCATION
`
`
`
`
`
`NO
`CLEAR SEARCH SCRATCH PAD
`
`RETURN
`
`196
`
`FIC. 8
`
`2
`
`A
`
`3
`
`a
`
`4.
`
`C
`
`5
`
`B I
`
`6
`
`b
`
`7
`
`D
`
`9
`
`8
`
`F | E
`
`Dell Inc., Ex. 1026
`Page 7 of 14
`
`

`

`U.S. Patent
`
`Feb. 27, 2001
`
`Sheet 6 of 6
`
`US 6,195,532 B1
`
`FIG. 9
`
`
`
`|
`
`PRIORITY
`1
`
`|
`
`FREQ
`
`|
`
`COUNTER
`
`FIC, 1 O
`
`PRIORITY
`
`SOC
`
`SID
`
`SID
`
`SID
`
`SID
`
`
`
`Dell Inc., Ex. 1026
`Page 8 of 14
`
`

`

`US 6,195,532 B1
`
`1
`METHOD FOR CATEGORIZATION OF
`MULTIPLE PROVIDERS IN A WIRELESS
`COMMUNICATIONS SERVICE
`ENVIRONMENT
`
`2
`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 with the 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 consist 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 portion. The control channels transmit information
`such as an SOC (System Operator Code), an 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. Com
`munication channels carry voice or data communications,
`where each channel consists of an uplink and downlink
`communications link. Presently there are Several cellular
`communication Standards. An analog Standard known as
`EIA/TIA553 was built upon the AMPS (Advanced Mobile
`Phone Service) standard. This standard Supports 21 analog
`control channels (ACC) and several hundred 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 traffic
`channel (DTC). The AVC or DTC are used for actual
`communications, and the ACC is used to transfer informa
`tion relating to, for example, call Set-ups, Service provider
`identification, and the other overhead or System information.
`A newer standard, the EIA/TIA IS136 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, and other System overhead information
`carried on the digital control channel.
`When a mobile communication 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
`up-link control channel.
`FIG. 2 illustrates a map of the United States illustrating
`cities such as Seattle, Chicago and Washington, D.C. For
`example, in Seattle 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 equal to 57, and that band B has been
`licensed to SOC 003 with a SID of 51. In Washington, D.C.
`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
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`This application is related to commonly assigned U.S.
`patent application Ser. Nos. 08/672,907, filed Jun. 28, 1996
`entitled “Method For Optimal Selection Among Multiple
`Providers. In a Wireless Communications Service Environ
`ment' 08/969,710, filed Oct. 29, 1997, entitled “A Method
`For Selecting A Wireless Communications Service Provider
`In A Multi-Service Provider Environment', which is a
`continuation of application Ser. No. 08/570,905, filed Dec.
`12, 1995.
`BACKGROUND OF THE INVENTION
`The present invention relates to communications, more
`Specifically, communications in a multi-Service provider
`environment.
`FIG. 1 illustrates a portion of the radio frequency spec
`trum. Frequency range 10 centered around 800 MHZ has
`historically been known as the cellular frequency range and
`frequency range 12 centered about 1900 MHz is a newer
`defined frequency range associated with personal commu
`nication Services (PCS). Each range of frequencies, i.e., the
`cellular and PCs, are broken into two portions. In cellular
`frequency range 10, there is uplink portion 14 which is used
`for communications from a mobile communication device to
`a base station Such as a cellular base station. Portion 16 of
`cellular frequency range 10 is used for downlink
`communications, that is, communications from a cellular
`base Station to a mobile communication device. In a similar
`fashion, Portion 18 of PCS frequency range 12 is used for
`uplink communications, that is, communications from a
`mobile communication device to a base station. Portion 20
`of PCS frequency range 12 is used for downlink
`communications, i.e., communications from a base Station to
`a mobile communication device.
`Each of the frequency ranges are 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” in order to carry out 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 spectrums
`assigned to the Service providers are separated So as to not
`interfere with each other's communications and thereby
`enable two separate Service providers to provide Service in
`the Same geographic area. 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 where a different Service
`provider may use a particular frequency band for which it is
`licensed within a particular geographical area. The PCS
`bands are referred to as A, B, C, D, E and F. The Aband
`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 are approxi
`mately 30 MHz wide. The D band includes uplink band 62
`and downlink band 64. The E band includes uplink band 66
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Dell Inc., Ex. 1026
`Page 9 of 14
`
`

`

`3
`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 providers have different SIDS. If a particu
`lar 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 expen
`sive 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, D.C. 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 the service
`provider with which the Subscriber has a pre-arranged
`agreement. If for example, the Subscriber travels from
`Seattle to Chicago, when turning the phone on 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 eight 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. The digital control channels (DCCHs), which
`contain the SOC and SID, are not assigned to specific
`frequencies within a particular PCS band. As a result, the
`mobile communication device may find it necessary 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. As illustrated above, the process of searching for
`a particular Service provider is laborious and may require a
`period of time on the order of Several minutes.
`
`SUMMARY OF THE INVENTION
`An embodiment of the present invention provides a
`method or locating a particular or desirable communications
`Service provider in an environment having a plurality of
`Service providers. After power-up, a mobile communications
`device Such as a cellular telephone, checks the most recently
`used control channel to determine whether an optimal Ser
`Vice provider is available on that channel. If an optimal
`Service provider is not available or if that channel is not
`available, the mobile communication device performs a
`Search through frequency spectrum in a pre-determined
`order until an optimal or acceptable Service provider is
`located.
`In another embodiment of the invention, the frequency
`Spectrum is Searched in a pre-determined order that changes
`based on information entered by a mobile communication
`device distributor or mobile communication device user. In
`yet another embodiment of the invention, the pre
`determined order for Searching the Spectrum for Service
`providerS is updated by over the air programming. In Still
`another embodiment of the present invention, the pre
`determined order for Searching is based on the mobile
`communication device's operational history.
`In yet another embodiment of the invention, multiple
`Service provider categories may be identified by matching
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`US 6,195,532 B1
`
`4
`the SID or SOC broadcast on a control channel with infor
`mation Stored in communication device.
`In yet another embodiment of the invention, “alpha tags'
`may be displayed on the communication device identifying
`a particular Service class while the communication device is
`in idle or camping mode.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The accompanying drawings, referred to herein and con
`Stituting a part hereof, illustrate preferred embodiments of
`the invention, and, together with the description, Serve to
`explain the principles of the invention, wherein:
`FIG. 1 illustrates the frequency spectrum used for wire
`leSS communications,
`FIG. 2 illustrates service areas within the United States;
`FIG. 3 is a block diagram of a mobile communication
`device;
`FIG. 4 is a flow chart illustrating a spectrum Searching
`routine;
`FIG. 5 is a flow chart illustrating the global spectrum
`Search routine;
`FIG. 6 is a flow chart illustrating a periodic Search routine;
`FIG. 7 is a flow chart illustrating a received signal
`Strength Search routine;
`FIG. 8 illustrates a search Schedule;
`FIG. 9 illustrates a search schedule ordered by registration
`history;
`FIG. 10 illustrates a prioritized list of service providers;
`and
`FIG. 11 illustrates display of an alphanumeric tag on a
`mobile communication device.
`
`DETAILED DESCRIPTION OF THE DRAWINGS
`FIG. 3 illustrates a block diagram of a mobile communi
`cation device Such as a cellular telephone or personal
`communication device. Mobile communication device 10
`includes transceiver 12 which sends and receives signals
`from antenna 14. Mobile communication device 10 is con
`trolled by control system 14 which may include a micro
`processor or a microcomputer. Control System 14 uses
`memory 16 for Storing programs that are executed and for
`Storing information 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 16.
`Memory 16 may include Storage devices Such as random
`access memory (RAM), read only memory (ROM) and/or
`programmable read only memory (PROM). A user commu
`nicates with control system 14 via keypad 18. Control
`System 14 communicates information to the user Via display
`20. Display 20 may be used to display information such as
`Status information and items Such as telephone numbers
`entered via keypad 18. Sound information to be transmitted
`from the mobile communication device 10 is received via
`microphone 22, and Sound communications received by
`mobile communication device 10 are played to the user via
`Speaker 24.
`After initially powering-up, a mobile communication
`device locates a Service provider and registers with the
`Service provider. Recalling FIG. 1, Service providers are
`located at a plurality of frequency bands acroSS the radio
`Spectrum. In order to find a Service provider, the commu
`nication device Searches the Spectrum to find Service pro
`
`Dell Inc., Ex. 1026
`Page 10 of 14
`
`

`

`15
`
`S
`viders. The communications device examines received Ser
`vice provider code e.g., SOCs (Service Operator Code) or
`SIDS (System Identification Code) to determine whether the
`Service provider is an optimal, preferred or prohibited Ser
`Vice provider.
`FIG. 4 illustrates a process or program that control System
`14 executes in 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 powered down, was an optimal Service provider. This
`is determined by checking the SOC 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 optimal, Step 34
`is executed where System 14 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 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 10
`with the service provider. Step 40 is an idle state where
`control System 14 Simply monitors the control channel of the
`Service provider for communication System overhead infor
`mation and for paging information that may indicate an
`incoming 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 Spectrum Search 33 provides a preferred but not
`optimal Service provider. Periodically, Such as every 5
`minutes, Step 42 is executed to determine whether the
`non-optimal flag has been Set, if the non-optimal flag is not
`set, control system 14 returns to idle step 40. If the non
`optimal 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 providers while executing periodic Search
`routine 44. 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 14
`returns to an idle State by executing Step 40.
`FIG. 5 illustrates a flowchart of global spectrum search
`routine 33 which is executed by control system 14. At step
`60 it is determined whether the last control channel used by
`the mobile communication device was a personal commu
`nication Services related control channel, that is, a control
`65
`channel in the bands A through F. If the last control channel
`was not a PCS control channel, step 62 is executed. In step
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`45
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`50
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`55
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`60
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`US 6,195,532 B1
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`25
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`35
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`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 lock 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 SID is associated with an
`optimal Service provider, Step 72 is executed where the
`mobile communication device clears the non-optimal flags,
`registers with the communication Service provider, and then
`enters an idle state by executing step 40 of FIG. 4. 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 68 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 down
`loading the Search Schedule in Step 80, frequency bands
`previously Searched are removed from 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. 4 and the cellular band
`Search discussed with regard to Step 74 are removed from the
`Search Schedule. After the modified 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 RSS 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, 2.5 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 an DCCH the SOC
`or SID 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 to identify the location
`of the DCCHs associated with the DTC that has been
`received. In step 88, the mobile communication device tunes
`to the strongest DCCH of the digital control channels
`identified by the DL. In 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 service provider. After step 96, the communication
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`7
`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 unde
`sirable or prohibited service provider with the spectral
`location of the SOC's or SID's control 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 determined 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. In step 100 the mobile
`communication device registers with the best stored SOC or
`SID, that is, an 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. 4 is executed where
`the mobile communication device enters the idle State.
`It should be noted that the searching operation of FIGS.
`4 and 5 may be carried out in a simplified manner. With
`regard to FIG.4, control system 14 may execute step 33 after
`step 30 while always skipping steps 32, 34, 36 and 38. With
`regard to FIG. 5, control system 14 may start the global
`Spectrum Search with Step 78 while always skipping Steps
`60-74.
`FIG. 6 illustrates a flowchart for the periodic search
`routine executed by control system 14. 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
`where 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 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. 5, step 124 is a RSS
`routine of any PCS and cellular bands that are in the search
`Schedule. 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 2.5 MHz segment and above
`a minimum threshold, Such as -110 dBm, is Selected. In Step
`126 the Selected Signal is examined to determine if it is valid
`by conforming to one of the previously referenced Stan
`dards. 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 when the SOC or SID is extracted 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 n